Connection lost between Win7 and WinXP

Ok, I have a pretty unique setup but I'm hoping I can get some help here. I have 5 machines. The main machine I work from was just upgraded to Win7 Ultimate 64. The other 4 are WinXP Pro64. I have a setup where I create a lot of 3d content. During "rendering", those other 4 machines are grabbing data from the raid on machine 1 (win7), processing it, and sending data (images) back to machine 1. This worked great when machine 1 was only running winxp64. But since upgrading to Win7, I seem to be able to only allow 2 or 3 machines connected. Any more than that and either machine 1 crashes/freezes or the other 4 lose their connection to machine 1 entirely. Does anyone have any idea how to resolve something like this?

Oh and when the connection is lost, I can sometimes still VNC into those other 4 machines. So the vnc connection works but if I type in the address of the shared drive on machine1 via vnc on a win. explorer window on one othe other 4, I get an error that it can't find that machine! Which is weird because I have an open vnc connection to it.