YouTube Hangs my Ubuntu-10.04 HP-dv7

At 7:17pm on Mar 2 2011 Ubuntu-10.04.1 running on an HP dv7 (x86_64) ceased to be able to play YouTube videos. Both Chromium and FireFox get wedged. Hulu and other Flash services play without problems. But after a couple of seconds of playing a YouTube video, the screen goes black with white streaks. /var/log/kern.log goes into loop:

Mar  2 19:17:37 dv7 kernel: [ 8232.470145] [drm:radeon_fence_wait] *ERROR* fence(ffff8800b8044980:0x000097BA) 510ms timeout going to reset GPU
Mar  2 19:17:37 dv7 kernel: [ 8232.470157] radeon 0000:01:00.0: GPU softreset 
Mar  2 19:17:37 dv7 kernel: [ 8232.470164] radeon 0000:01:00.0:   R_008010_GRBM_STATUS=0xE53024A4
Mar  2 19:17:37 dv7 kernel: [ 8232.470171] radeon 0000:01:00.0:   R_008014_GRBM_STATUS2=0x00110002
Mar  2 19:17:37 dv7 kernel: [ 8232.470177] radeon 0000:01:00.0:   R_000E50_SRBM_STATUS=0x200000C0
Mar  2 19:17:37 dv7 kernel: [ 8232.470192] radeon 0000:01:00.0:   R_008020_GRBM_SOFT_RESET=0x00007FEE
Mar  2 19:17:37 dv7 kernel: [ 8232.470249] radeon 0000:01:00.0: R_008020_GRBM_SOFT_RESET=0x00000001
Mar  2 19:17:37 dv7 kernel: [ 8232.470314] radeon 0000:01:00.0:   R_000E60_SRBM_SOFT_RESET=0x00000402
Mar  2 19:17:37 dv7 kernel: [ 8232.519205] radeon 0000:01:00.0:   R_008010_GRBM_STATUS=0x00003028
Mar  2 19:17:37 dv7 kernel: [ 8232.519211] radeon 0000:01:00.0:   R_008014_GRBM_STATUS2=0x00000002
Mar  2 19:17:37 dv7 kernel: [ 8232.519217] radeon 0000:01:00.0:   R_000E50_SRBM_STATUS=0x200000C0
Mar  2 19:17:37 dv7 kernel: [ 8232.523318] [drm:radeon_fence_wait] *ERROR* fence(ffff8800b8044980:0x000097BA) 570ms timeout
Mar  2 19:17:37 dv7 kernel: [ 8232.523320] [drm:radeon_fence_wait] *ERROR* last signaled fence(0x000097BA)
Mar  2 19:17:39 dv7 kernel: [ 8235.040219] [drm:radeon_fence_wait] *ERROR* fence(ffff8800c4203ac0:0x000097C3) 510ms timeout going to reset GPU
Mar  2 19:17:39 dv7 kernel: [ 8235.040231] radeon 0000:01:00.0: GPU softreset 
Mar  2 19:17:39 dv7 kernel: [ 8235.040238] radeon 0000:01:00.0:   R_008010_GRBM_STATUS=0xA0003028
Mar  2 19:17:39 dv7 kernel: [ 8235.040245] radeon 0000:01:00.0:   R_008014_GRBM_STATUS2=0x00000002
Mar  2 19:17:39 dv7 kernel: [ 8235.040251] radeon 0000:01:00.0:   R_000E50_SRBM_STATUS=0x200000C0
Mar  2 19:17:39 dv7 kernel: [ 8235.040263] radeon 0000:01:00.0:   R_008020_GRBM_SOFT_RESET=0x00007FEE
Mar  2 19:17:39 dv7 kernel: [ 8235.040319] radeon 0000:01:00.0: R_008020_GRBM_SOFT_RESET=0x00000001
Mar  2 19:17:39 dv7 kernel: [ 8235.040384] radeon 0000:01:00.0:   R_000E60_SRBM_SOFT_RESET=0x00000402
Mar  2 19:17:39 dv7 kernel: [ 8235.089275] radeon 0000:01:00.0:   R_008010_GRBM_STATUS=0x00003028
Mar  2 19:17:39 dv7 kernel: [ 8235.089280] radeon 0000:01:00.0:   R_008014_GRBM_STATUS2=0x00000002
Mar  2 19:17:39 dv7 kernel: [ 8235.089286] radeon 0000:01:00.0:   R_000E50_SRBM_STATUS=0x200000C0
Mar  2 19:17:39 dv7 kernel: [ 8235.091966] [drm:radeon_fence_wait] *ERROR* fence(ffff8800c4203ac0:0x000097C3) 570ms timeout
Mar  2 19:17:39 dv7 kernel: [ 8235.091968] [drm:radeon_fence_wait] *ERROR* last signaled fence(0x000097C3)
Mar  2 19:17:42 dv7 kernel: [ 8237.611578] [drm:radeon_fence_wait] *ERROR* fence(ffff8800c4203f00:0x000097CA) 510ms timeout going to reset GPU
Mar  2 19:17:42 dv7 kernel: [ 8237.611591] radeon 0000:01:00.0: GPU softreset 

Reinstalling Flash didn't help. Eight hours earlier, I had updated to 2.6.32-29-generic; but booting with the previous kernel version doesn't help. Installing the "linux-firmware-nonfree" drivers made no difference.

Start-Date: 2011-03-02  10:42:14
Install: linux-headers-2.6.32-29-generic (2.6.32-29.58), linux-headers-2.6.32-29 (2.6.32-29.58), linux-image-2.6.32-29-generic (2.6.32-29.58)
Upgrade: linux-generic (2.6.32.28.32, 2.6.32.29.35), linux-headers-generic (2.6.32.28.32, 2.6.32.29.35), linux-image-generic (2.6.32.28.32, 2.6.32.29.35), linux-libc-dev (2.6.32-28.55, 2.6.32-29.58)
End-Date: 2011-03-02  10:43:29

What has changed to cause this?
Others with the same problem are posting to
http://ubuntuforums.org/showthread.php?t=1699550

Fix Pink / Red YouTube Videos Bug Using Flash 10.2 In Ubuntu
"Possible fix 3" solved the problem by disabling "hardware acceleration" in Flash. So who's bug is this? Is the bug in Flash 10.2 or something it calls? In any case, plugins shouldn't be able to crash X11. So X11 is behaving badly; but the errors show up in "kern.log"; does the kernel deserve some of the blame?