Comment 1 for bug 155312

I have the same issue, on a Toshiba Satellite A55 laptop with an Intel 855GM graphics card. Also using i810 as the X module, and i915 for the kernel. I also have the same "f000:5503: 01 ILLEGAL EXTENDED X86 OPCODE!" line in the X log file. xserver-xorg-core and kernel are the same versions as above, too, 2:1.3.0.0.dfsg-12ubuntu8 and 2.6.22-14-generic. Upgraded to Gutsy (Xubuntu) two days ago.

I did a test this afternoon to see exactly how the screensaver brings it about. I turned it on, logged into Fluxbox, then let it sit. After 10 minutes, my plain black screensaver came up, then the screen appears to power down after another 10 minutes, like it has always done. I waited for about two hours after that, without giving it any input, and the screen remained off with no changes. After that, I moved the mouse around to get the screen back. 10 minutes went by, and it went to the screensaver. However, after another 10 minutes, instead of the screen shutting down, the screensaver deactivates and the lockup occurs.

So basically, it happens when it tries to power down the screen from the screensaver for the second time.