dual nics

I have 2 network cards in a 2003 web edition server with all the latest updates. Network card A is connected to my domain and works just fine. Network card B is connected to a T1 for an external website. The problem is that network card B doesn?t disconnect but packets stop transmitting and the website goes down. So I have been repairing the connection and then it works fine for 6 hours or so depends on the day. They both have static IPs. Any suggestion would be great.