MYSql (possibly) crashing server

About 10 days ago my debian server started crashing quite regularly.
Aparently it was crashing when cron was attempting to run mysqldump.
I was not 100% sure that this was the cause, but it looked mysql
related.
The really bad part was that some tables needed repair, and that was not
a
very pleasant thing, since some data was lost in the process.
After the server rebooted 3 nights in a row, I have upgraded mysql from
5.0.16 to 5.0.18 and for 10 days everything was ok.
2 hours ago the server crashed again (several hours before the mysqldump
script is ran)
Has anyone experienced something similar? I could really use some
advices.
Since I don’t have physical access to the server I couldn’t really run
fsck
on /var (because it did not want to umount /var nicely, and I was
reluctant
to use umount -f, fearing that I would end up with a box that I cannot
access)
Thanks,
Bogdan