connection lost

I have an XP station and my server is 2000. I have designated some files on the server to be available offline. Now every little bit I get a message that I am working offline and that the server is no longer available. If I try to open the mappeddrive it will only show the offline folders, but if I tell the synch manager to go ahead and synch it works just fine and I’m reconnected. Is something timing out? I have looked and looked in knowledge base and found zip. Thanks!