I can confirm the same bug.
Ubuntu natty narwhal with
2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:50 UTC 2011 i686 athlon i386 GNU/Linux
Ati Radeon card with Chipset: "ATI Radeon 9600XT AR (AGP)" (ChipID = 0x4152)
systems run 10-30mins and dies.
Adding this xorg.conf seems to fix the problem
Section "Device" Identifier "Radeoni" Driver "radeon" Option "EnablePageFlip" "false" EndSection
I can confirm the same bug.
Ubuntu natty narwhal with
2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:50 UTC 2011 i686 athlon i386 GNU/Linux
Ati Radeon card with Chipset: "ATI Radeon 9600XT AR (AGP)" (ChipID = 0x4152)
systems run 10-30mins and dies.
Adding this xorg.conf seems to fix the problem
Section "Device"
Identifier "Radeoni"
Driver "radeon"
Option "EnablePageFlip" "false"
EndSection