Wednesday, August 31, 2011

Blank screen after Windows logo: Apparent broken video card

I got a call from my wife while I was at work yesterday: There was a problem with our primary home PC, which runs Windows 7.  As the machine was booting, after the BIOS data appeared followed by the graphical Windows 7 “loading” logo on the primary monitor, the primary monitor went into sleep mode (as though it had been unplugged from the PC).  By moving the mouse around, the mouse cursor was visible on the secondary monitor, but clicking it (including right-click) didn't do anything.

Getting home, I saw the problem for myself.  I concluded that the Windows logon screen was being displayed on the primary monitor -- I just couldn't see it because the primary monitor was off.  I was able to log onto the machine blind (by arrowing over to my user profile, hitting Enter to activate it, keying in my password, and hitting enter again to log in).  Once in to Windows, I was able to make my secondary monitor become the primary monitor, via right-click on the desktop, selecting Screen Resolution from the Right-click menu, “rescuing” the Screen Resolution window from the sleeping primary monitor onto the secondary monitor to make it visible, then checking the “Make this my main display” checkbox on the secondary monitor.

I spent pretty much the entire evening troubleshooting the problem.  Here the long list of troubleshooting steps I tried:

Verify both ends of the monitor cable were firmly seated: It was seated properly.

Cold reboot: No change in behavior.

Install the latest video driver (for the video card, an NVidia Geforce 6800 GT): No change in behavior.

Install the latest monitor driver (for the primary monitor, a ViewSonic VX2035wm connected via DVI): No change in behavior.

Uninstall the monitor drivers (and let Windows reinstall them after rebooting): No change in behavior.

Uninstall Microsoft Security Essentials (which I had just recently installed) (on the theory that MSE could somehow be seeing the ViewSonic monitor driver as malware): No change in behavior.  (I reinstalled MSE again afterwards.)

Restore the system to a restore point from a few days prior (when I know the monitor had been working fine): No change in behavior.

Reboot into Windows Safe Mode: This actually did get the logon screen, and then the Windows desktop, to display properly on the primary monitor.  I was even able to increase the screen resolution from the safe mode default (1024x768, I think) back to the native resolution of 1680x1050.  I was not able to use dual-monitor display, though; the Screen Resolution dialog only detected the primary monitor while in Safe Mode.  Rebooting again (back into normal mode) brought me back to square one.

Uninstall the video driver (then reboot): After rebooting, the behavior was similar to safe mode; the primary monitor worked, but not the secondary.  Upon reinstalling the NVidia video driver and rebooting once more, it was again back to square one.

Reseat the video card (with the PC powered off, then boot back up): No change in behavior.

Unplug the secondary monitor (leaving only the primary monitor plugged in) (then reboot): This didn’t help.  I still got, after rebooting, the BIOS information visible, the graphical Windows 7 logo visible, then blank screen / sleeping monitor.

Swap the ports that the two monitors’ DVI cables were plugged into, then reboot: This actually caused me not to get anything display on either monitor.  I changed it back afterward.

Check BIOS settings: I didn’t notice anything unusual, or any settings that I could change that might be likely to fix the problem.  I ended up leaving everything alone.

Finally, after all that, I hit upon a good solution: I replaced the video card.  Specifically, (after powering both machines down and unplugging them, of course), I pulled the GeForce 6800 GT from my primary machine and set it aside; then, I pulled the GeForce GT 430 from my HTPC (leaving that PC with just the motherboard’s onboard audio/video), and installed that card in my primary PC; then I booted the primary PC back up.  After doing that, and letting Windows install the NVidia display driver, both monitors came up with no problem.

So even though I had been pretty convinced initially that I was looking at a software problem, probably a driver problem of some kind (given that the primary monitor worked fine at boot time, and even displayed the graphical windows logo, and also worked fine in Safe Mode), the problem apparently was that my GeForce 6800 GT decided to (partially) fail on me.  It was actually my lovely wife that made the astute observation that the fact that I had been fairly recently running that card at a scorching hot 100+ degrees C probably hadn’t helped matters!

Note that I don’t recommend that anyone else who encounters this issue (and comes across this blog post via a search) run out and spend $$$ to replace your video card as your first option.  In researching this issue online during the course of the troubleshooting, I did run across some reports from others of this same problem (screen goes blank after displaying the Windows logo during boot) who were able to solve their issue by doing one of the other steps that I tried, such as uninstalling and reinstalling video drivers.

For the time being, I’m in good shape with my workaround.  The lower-end but newer GeForce GT 430 is actually almost as good a video card as the original 6800 GT; and the HTPC can play TV and movies fine with the onboard video.  I guess this gives me something to put on my birthday list for my birthday coming up later this year!

Friday, August 26, 2011

Firefox: The case of the corrupted cursor

At work, I recently had the chance to upgrade to a new development laptop PC, a Thinkpad T520 running Windows 7.  The machine is excellent, with one weird exception: In Firefox (and only in Firefox), when keying in text into a text entry field in a web page or into the browser address bar, the caret (i.e. the text entry cursor) would sometimes appear to be “distorted” or “corrupted” – that is, some “garbage” pixels would appear around the caret whenever I moved it (either by typing in a character, or by using the arrow keys). 

Problem Details

The problem is hard to explain, so here’s a screen capture of a particularly severe example that occurred when I was entering text into a textarea.  The caret in this cropped screen shot is between the “2” and “5” in “8/25/2011”; note all the other weird stray black and white marks in the text.  (I added the red oval to the screen capture to show the area in which the “corruption” was appearing.

firefox caret garbage - crop

After waiting a little less than a second without moving the caret, the problem would go away – the “corruption” would disappear from the display.  However, the problem would come right back upon moving the caret again.

The caret itself would also sometimes not appear until the “corruption” went away, which made text editing surprisingly difficult – a frustrating problem.


The problem would only occur in Firefox, not in other browsers such as Internet Explorer 9, or in any other applications I tried (such as Eclipse, Word, and Notepad).

Experimenting, I found that the problem would not occur when Firefox was started in Safe Mode (via Firefox menu | Help menu | Restart with Add-ons Disabled).  However, I tried running Firefox in normal mode with all extensions and add-ons manually disabled, and that didn’t help.  I tried setting up a new Firefox user profile, and that didn’t help either.

I also noticed that beyond the issues with the caret, the actual rendering/shape of letter character glyphs being typed into Firefox was affected.  The  characters themselves appeared “wrong” when Firefox was running in normal mode, but they appeared normally with Firefox in safe mode.  Here are two cropped screen shots I took of a bunch of “f” characters being entered in to the address bar, the first in normal mode, the latter in safe mode:

firefox address bar standard

firefox address bar safe mode

Here’s a zoomed-in view (again, normal mode first, then safe mode):



Note that in the former image (Firefox normal mode), the “f” glyphs do not appear the same as one another and have some faint red/yellow/blue/green aliasing (blurring), whereas in the latter screen capture (Firefox safe mode) each “f” glyph is identical and has no aliasing (look at the unzoomed image).

At this point I was suspicious of some kind of issue with my video card.  The normal first course of action with a suspected video card behavior issue would be to update video card drivers.  When I checked, though, I found that I was already running the latest drivers for my video card (an NVidia NVS 4200M).

Google was initially no help; all the searches that I tried for terms like “firefox cursor corruption” or “firefox caret appearance” resulted in pages talking about the Firefox caret navigation feature (F7 key), which was not the issue here.


I hit upon the solution when I changed angles of attack and Googled for “firefox safe mode”.  The first result was a Firefox help article describing safe mode, which linked to a Mozillazine knowledge base article with more details on Firefox safe mode. That article in turn had a list of about a dozen bug repots related to safe mode, one of which was Bug 591139 - Disable hardware acceleration in safe mode. Aha – that sounded like a video-related issue!  Reading through that ticket, I learned that starting in Firefox 4, a feature called “hardware acceleration” (with which I was previously unfamiliar) is disabled when Firefox is in safe mode.

Hitting up Google once more, this time for “firefox disable hardware acceleration,” I was led to a setting in the Firefox options menu: Firefox menu | Options | Advanced | General tab | Use hardware acceleration when available

I unchecked that setting, restarted Firefox, and that did it – the problems with the caret corruption/garbage and the malformed character glyphs no longer occurred!

So apparently Firefox has an on-by-default feature where it uses hardware acceleration, presumably from the local PC’s video card, further presumably to improve its performance and/or ease load on the primary CPU.  However, having disabled this setting, I haven’t noticed any appreciable difference in performance.

I don’t know who is to blame for this issue – bad video driver, bad video hardware, Firefox itself, some combination of those, or something else entirely – but for the time being, I’m just satisfied that the issue is resolved for me!

I hope this saves some frustration and/or troubleshooting time for anyone else experiencing this odd issue!

Wednesday, August 03, 2011

Key Jammin’, Circa 1950!

While helping my Mom clean out her basement in preparation for a move recently, I came across the apparent answer to the mystery of why some older fixed-width fonts confusingly feature “1” (numeral one) and “l” (lowercase letter L) glyphs that are identical:


(Hint: Look to the left of the “2” key!  Anything missing there?)