We've got an Ubuntu 11.10 server which we use for LAMP web development here in the office. A couple of times in the past, it's gone through a phase where it reboots after it's been up for one hour. It's not a specific minute within an hour - it's just after one hour of uptime.

The last time this happened it seemed to fix itself after an apt-get update / upgrade on the installed packages. I've done this again just now and it doesn't seem to be helping. Still reboots. I can't use acpi to get any temperature readings as the machine either doesn't have sensors, or those it does have aren't visible to the install.

Ordinarily I could take a little extra time to fix this (we're primarily a Windows developer and the Linux box is kind of my baby) but I'm working on a MASSIVE PHP project right now and need this fixed in a hurry so a dist upgrade isn't really an option right now.

Anyone got any thoughts on things I could try, or look at? All help appreciated.