After updating to Ubuntu 11.04 my computer started to turn off and reboot. This happens about every half hour, I think there is a tendency for it to happen when I work with multiple applications at once.
It is both my Desktop and Laptop.
I have installed BOINE Manager, PlayOnLinux, Gimp, Qt, Wine, VLC-player and Blender. Otherwise is all as default.
See my /var/log/kern.log.1 here: http://paste.ubuntu.com/608690
When I run Memtest 86+ I get this error:
This is a very only post, but since the question is still active, I'll leave my recommendation to future users with this/similar problem:
Taking into account the print-screen provided, hardware failure is what's causing Ubuntu to restart "just like that":
Memory errors may lead to an unstable system, thus rebooting it when accessing bad memory blocks.
When you used Memtest 86+, the application was giving you that error, saying that you have bad memory blocks at that address.
I've written an answer with a solution to mark does address to prevent the system from using them: Exclude bad ram bytes.
Like this you can continue to use you memory modules even with damage addresses. The alternative is to acquire a new memory module.
CPU temperature, if it gets over the fail-safe limit, then the motherboard sends the kill signal to shutdown the computer immediately. This is done to prevent hardware meltdown.
A side effect for a defected cooling system is the overheating of you CPU, what in turn leads to other hardware problems. (very unlikely, but under certain circumstances, may justify your memory issues).
Here, the solution is as simple as to clean up your fans and place some new thermal paste on your CPU.
/var/log/kern.log.1into Ubuntu Pastebin immediately after the reboot occurs and edit you question to include the link? Thanks! – ændrük May 12 '11 at 20:55