It looks like an hardware issue.
The first thing to do is :
check logs :
system.log and kernel.log.
Mostly it's an hardware failure as :
- Broken fans, so the cpu become hotter (try $acpi -V)
- Memory corruption (see above)
The things you can do are also :
test disk ($fsk)
check you ram =
you will have the total of memory under "used" column :
used free shared buffers cached
Mem: 3369312 3242568
now do :
$ dd if=/dev/urandom bs=768304 of=/tmp/memtest count=1050
$ md5sum /tmp/memtest; md5sum /tmp/memtest; md5sum /tmp/memtest
if the checksum do not match, that mean you have a memory failure
Check the network also. Do it work ?
With these steps, you should have at list a piece of info