Unable To Browse An Intranet Computer

I have been stuck in a strange problems which happens occasionally--but too often to be ignored.I have a Windows 2003 Server running as a virtual machine via MS Virtual PC 2007. The host machine is a Windows 7 Home Premium 64-bit. This setup used to run fine where I had no issues accessing the guest OS (Win 2003). My development environment is Visual Studio 2005 and 2010 based, both running on the host machine.Some days ago I started working on a ASP .NET application which had a lots of files on the guest OS. That would cause the dreaded 'Network Bios Limit Reached' error in VS. So tweaked a few Registry keys on both host and guest and that problem went away. But then I started to get a new kind of problem: Occasionally, within VS 2010, I could not save files and that would be so bad that the entire guest OS cannot be browsed (but can be seen in the Network Neighborhood and be pinged as well).I have undone all Registry changes in both guest and host but I still see this problem. Only the virtual machine running Win 2003 is occasionally un-browseable but still ping-able by other intranet computers: Win xp, vista, Win 7 but cannot browse until the guest win 2003 is re-started.Is it some kind of network buffer being too full? So far I only see this problem when working inside Visual Studio 2010 but it could be happening elsewhere. The guest win 2003 is assigned a static ip of 192.168.1.7 by the router, btw.