Randomly crashing server

[Emil]

Hi,

I'm having quite a panic to say the least. I have a webserver that has
started to crash every 1-2 hour. It has worked fine from when I
installed it like 5 month ago but yesterday it started crashing. I need
it working like now.

I haven't a whole lot of experience with what to do. The config is a
host with ubuntu 8.04 and virtualbox. The guest is ubuntu 8.10 running
apache, etc. It's virtualbox that is crashing, but I don't think it's
virtualbox fault but the guest ubuntu that is crashing. I might be a bit
tight on ram (1GB total and 512MB for the guest) but that config has
worked for years. I also have space on the hard drives so that's not it.
I've tried looking in a couple of logs in /var/log like sysslog but
haven't really found anything I find suspicious (I'm not sure what to
look for though). I've checked top and can't find anything special.

Any ideas are very very very welcome.

Kind Regards,
Emil, Sweden