Network Drives keep getting disconnected?

I have this recurring problem which is doesnt seem to make sense.My Server keeps Disconnecting the network drives for no apparent reason.Now since i havent found any other solution i have to restart it so it can reconnect them. I'm running Server 2003 R2,on a Wireless network. The thing is when there is no internet,this problem ceases. but once the internet comes back,it starts happening...which suggests that it is internet related.and nowadays its quite a couple of times in one day.i have run a virus scan on both the server and the clients,but havent found anything. and when the network goes down, there is no indication on the client computers. The only time u realise it when u try to acess something from the server, and its unavailable, but your connection to the Router is fine. The clients run XP Proffesional. we running Microsoft Exchange for outlook.any ideas?

Network Drives keep getting disconnected?
We more or less the same problem when we switched to Exchange a short time ago. In our case we lost the connection to the network drives from the client machines. It would show the drive but as disconnected. We did everything but reload XP, didn't make a difference. Finally we removed anti virus from client machines then reloaded and updated Symantic and the problem went away. Have had no problems since then. Have no idea why it was doing it though.