I have been running Ubuntu for a week and it's been pretty painful so far, but I would really like to leave Windows for Ubuntu, because it's free, open-source and all that is good.
Ubuntu always logs my computer out within 10 minutes when I am using it. The log-out often combines with an 'enter'-keystroke. After logging in again, the issue will not return. After a reboot, within 10 minutes, X will crash when using it.
You can view the logfile at http://www.codepad.eu/view/raw/70522425, but hasn't helped me much in tracing the issue.