Traveler:
Good suggestions by Merlin and Mac as always.
One thing i like to do in situations like this is use the process of elimination. To rule out the network configuration or hardware as the cause of the problem, power off the old computer, disconnect the it from the router, and power it up. Use it for some time to see if it locks up, still. If it does, the network connection is not the cause and we need to tell you what to do next to determine what is the cause. If it doesn't lock up, then the network software or hardware may be the culprit.
Let us know how it goes so we may tell you what to do next.
Regards,
Doc