networking question - switched out harddrives between machines

[Linda]

I have a machine that was acting flakey and a clone used for software 
development. The flakey machine keeps hanging on the motherboard 
flashboard when I have to shutdown for the kernal updates. I had the 
bright idea to switch the hard drives so the flakey machine would be 
used for less critical purposes.  When I ran the switch I can ping 
across the network, but I can't mount Network File Systems and I can't 
ssh. I'm thinking it is because the NIC changed. Does this sound 
plausiable? If so how do I go about fixing it?
                  Thanks
                   Linda
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