Server freezing up and cannot clear ARP Cache

I am running an Exchange Server (2003) on a MS Server 2003 (PDC).
Every so often, the whole system looses it’s network connectivity.
I cannot log in remotely, my users can no longer access the internet, and the server service cannot be retarted.
I end up having to restart the server itself.
Once I do that, I may or maynot be able to connect again.
After a 2nd restart, all is well.
I tried to repair the NIC, but get an error that it could not repair the NIC connection, as it could not clear the ARP cache.
Not sure if the two are actually related or not, but it is an issue it seems to me.