[CentOS] System drops off network after a few minutes

I have an Intel SE7525RP2 motherboard with a Yukon Marvel (82541GB controller) NIC in it. After installing CentOS 5.1 it functions fine for some minutes then looses network connectivity. By coincidence, I was using the system to clean some HD's for another and had booted off Knoppix and noticed it never exhibited this behavior, the network remained functional even overnight when I returned to the system?

I looked through messages and didn't see anything NIC/network related, can anyone suggest something to check?

Thanks!
jlc
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