Arbitrary Warmstarts!

[Erwin Ambrosch|XHOSTPLUS <erwin.ambrosch@xhostplus.at>]

Hi all,

one of my Linux servers (debian etch with Kernel 2.6.22-4-686 from 
backports.org) does arbitrary warmstarts (like one is pressing the reset 
switch).
I had the same symptom with the 2.6.18-6-686 kernel.
Can one tell me whether there are conditions under which linux performs 
a warmstart.
I have not configured to reboot in case of a kernel-panic. Temperature 
of the CPU is normal. The FANs are working.
I checked logfiles, but did not find anything.
I also ran chkrootkit which did not find a problem.

The first reboot (warmstart) was on the 7'th of may. Until this date it 
worked perfectly for 3 1/2 years.

Did one have such a symptom?
Could it be that the machine is compromised?

Thanks in advance
Erwin