orasrv hangs once in a while

Hi folks

I'm experiencing a strange behaviour of orasrv once in a while: Sometimes it just stops working. All clients which try to get a new connection to the database via sql*net v1 then hang to. This happens sometimes once or twice a day, sometimes not at all.
After killing the orasrv, and restarting it afterwards, everything works fine, at least for some time.

I'm experiencing this which all versions of oracle. It occurred with 7.0.12, 7.0.16, 7.1.3 and 7.1.4. Didn't try 7.1.6 yet.

The problem occurs in a net with a SUN Server running Solaris 2.3 and 2.4, and Clients running WfW with Sunselect PCNFS and SQL*NET V1.

Has anyone experienced something like this too ? Any hints, tricks, clues ?

Thanks , Richard