Network drives show up as disconnected.

I have a lab that when users logon on their H drive shows up but says disconnected. How ever the two other drives show up and work fine. It seams to be a random thing as some users are able to access their H drive and others are not. I can see it being a issue with time. As right after they logo on their drive shows up as disconnected They are using windows Xp and the server is a windows 2003 server. I applied a GPO to always have windows wait for the network connection that dident fix it either. I am thinking it might be an issue with a GPO I setup to set windows IE to a defalt page. Any ideas?