PC Loses Network After 5 minutes

I’m running Windows XP. I connect to a network running Windows NT 4.0. After my computer boots up I can see everthing on the network. I can connect to our servers and grab files if I need them. However, after 5 or 10 minutes, my PC loses the abilityto connet to these servers and other workstations. What is going on? It tells me that it cannot find the specified path or I may not have permission to view the selected resources. Please help!!!