Ever since I edited the two registry entries as krbaugh suggested on 2/4/2010 I have not had a single case of this issue. I think he's totally right, the mass-consumer editions of Windows are not optimized for use as a file server. Windows 7 had big improvements, but only when sharing with itself. Making it easy or obvious how to change that might undercut their marketing of Windows Home Server (which is already dying off). As I mentioned, Windows 7 actually does work well if you're ONLY sharing files with other Windows 7 users, which probably lines up with their strategy of dropping support for their older OSs.