Can’t connect to a network computer when it has a specific name

Hi. I have a network with 2 xp computers, 3 vista and a xp file server named server1. After working fine for a year the vista computers were suddenly unable to connect to the server by name. They could connect by IP but the software they run requires a named path. I exhausted all possible solutions found on the net. So – I wiped out the server and installed vista on it. The problem is STILL there. The xp computers can connect but not the vista ones. If I change the name to serverX everything connects but their database has the name server1 hardcoded into it. Ideas anyone?