After 2 hours the system reboots itself
I updated the system to karmic koala via the button in the update manager on the release day of Karmic. Now after switching on the computer (a netbook medion Akoya mini E1210 similar to a MSI-wind) after exactly 2 hours the system switches from the X window screen back to the tty screen and reboots. This rebooting occurs without going back to grub. As far as I know I have not changed anything which would provoke this. I have seen this behaviour now on a consistent basis. It happens always after 2 hours of starting the system. Please guide me in providing more information.
lsb_release -rd reveals
Description: Ubuntu 9.10