network neighborhood fails

I have a client that has a peer to peer network with 98, 2000, and me. The problem is that network neighborhood quits functioning and suddenly starts functioning again. During the time that network neighborhood is not functioning all of his mappeddrives work. Also, he sometimes has off and on slow file transfers.

I have reset the 10/100 switch and it may start to function and may not.

I am of the mind that I have a bad nic, but I’m not sure how I can test them. The customer has ADSL router uplinked to a 16 port 10/100 switch.