After a long and bloody battle, I have put down my sword and knelt at the feet of Vista.  A voice called to me, as if in a dream, and asked me what I was thinking to expect that an upgrade would simply work, especially considering that Visual Studio had gone from 2003 to 2005 from an upgrade, and then a service pack, and then the vista service pack after the upgrade.  Considering that the problem is only affecting sites with source control on it, I can't be the only one having this problem, and yet Microsoft has no reported cases.  So maybe it's just me.  Add some intermittent connectivity issues and "driver could not be loaded" errors, and, well, I can respect when I'm beaten.  So I've been backing my thang up and a clean install will begin shortly.