Help! Domino 6.0.2 CF2 on SuSE 8.0 hangs

Hi!

We have Domino 6.0.2 CF2 on SuSE 8.0.

There are smtp, pop3, http and Symantec antivirus tasks on domino server.

Domino server hang several times in a day, mostly at night.

What can be a reason of this?

thanks