I've got 3 XP PC's connecting to 2 server a 2000 and NT4 when loggin on, which is fine, however after about 45 minutes XP seem to lose their connection to the NT4 but still can access the 2000 server.  I've the power management setting and they all seem to be fine.  I've got another 5 XP PC's logging onto the network remotely via the Remote Desktop Connection and they work absolutely fine.  Does anyone out there have any idea as to what could be causing the XP's to lose their connection to the NT4 server.

Many Thanks for any help in advance.