No Inbound Traffic

Hi,
I am currently having a bit of a problem with a Windows Server 2003 server
that I am trying to setup to run a few game servers for myself and friends.
What happens is that the server after running for a certain amount of time
doesn't drop all network activity but the inbound traffic will not work. I
have had Redbus login to the machine locally and everything is working fine
and my RTG graphs show constant outbound traffic but the inbound is just
dead. I was wondering if anyone knew of problems like this and what can fix
it before I resort to a reformat.

Thanks.

Forgot to mention that after a reboot the machine comes back online and
works perfectly for a while and then the same happens.