connections fail

[Hagen NornagestKühl]

Hi everyone,
My desktop box runs FreeBSD 5.3 and I have a problem with opera (7.54)
and sylpheed-claws (1.0.0).
When these applications run for quite a while(some days) they can't
establish any connections.
If I restart the application it works again.
Has anyone seen these or similar problems, or any idea what to do?
I hope the information given is enough, though it isn't very much.

Thanks in advance

Hagen Kühl