sort of hangs

[trondhuso]

For some reason my server - setup using perfect server for ISPConfig 2 - just hangs. cannot access it with ssh, webserver is not accessable, and mail hangs.
I can see that the server is "running" with ping, but that is all.

This is running as a vds and the provider tells me that something is doing a lot.

The only way for me to get access is to restarting the server...

this happens every three months... almost on the same date...

Is there something I can do to prevent this? What to look for in logs?

It's running 8.04, so I know that the version is quite old. I'd like to upgrade, but I am not sure if I want to... When "work" why fix - right?