I have been using ubuntu 11.04 beta for the past two months... I needed to use it because of the repositories/extensions exclusive to that build.
Every so often however (sometimes every few hours, sometimes every few weeks) it will randomly shut down.
At first I thought it had to do with the mild overclocking I had in place. So I removed it.
Everything was fine for a few weeks, and I just woke up to it being off again. Quite annoying!
Anybody know what could be the cause?