System info: up-to-date 32-bit 6.06 LTS with 2.6.15-27 kernel on a ST20G5 (AMD Athlon and Radeon X200 chipset with IGP)
I am experiencing occasional system freezes. It happens in X only -- the entire screen goes white and the computer does not respond any more to anything but a power-cycle. I had the same issue in Breezy, then switched to Gentoo 2006.0 where everything worked fine, and now that I'm back to Dapper, so is this problem.
I've had this happen with open-source Radeon driver on Dapper and ATI's fglrx drivers and the generic VESA on Breezy. As I already mentioned, this did not happen on Gentoo (both 2.6.15 and 2.6.16 kernels) nor on Windows XP sp2 (dual-boot).
There are no kernel panic messages on the screen that might indicate the source of the problem nor is there anything in the logs. I have suspected hardware fault, but I can run memtest for hours with no reported errors, and I drive the machine much harder in Windows XP than I do in Ubuntu and it never crashes.
I will post separately the output from dmesg and lspci, as well as the information from /proc.
Kernel info