[ubuntu] Sudden black screen with no error message

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http://ubuntuforums.org – Hi! I'm running 11.10 on a 32 bit, 2 year old Lenovo thinkpad. About once ever 10 hours of usage, my screen becomes black with no error message, but the computer and monitor are still on. Hitting various keys, CTRL-ALT-DEL, mouse buttons, etc. don't do anything. When I pull the plug, it reboots fine. I have a dual boot system and didn't run into this problem on Windows 7 for over two weeks, so I assume it's a linux issue. I also had the same issue using 12.04, also dual-boot, so I downgraded to 11.10, with no luck. The last time this happened, I was running IDLE for python development a (Hardware)