After Windows logout/login, TBB3.0b1 complains it can't start Vidalia

I have TBB3.0b1 installed on 2 different Windows 7 machines. After installing, I am able to launch it normally, and quit TBB and relaunch it fine on both. But on (only) one of them, if I quit TBB, log out of Windows then log back in, TBB will fail to launch, showing a dialog box titled "Error" and containing the text "Unable to start Vidalia". If I don't log out of Windows, I can quit and restart TBB normally on that machine. If I reinstall TBB3.0b1 (either a clean install or reinstalling over the problem install), I can start TBB normally... until the next time I log out of Windows.

I started with a clean install of TBB3.0b1 on both machines, and it is installed in the same location on both (C:\Users[myusername]\AppData\Roaming\Tor Browser). I'm not sure if this is relevant, but a big difference between the two machines is that I am logging in to a local account on the machine that doesn't have this problem, and to a domain account on the machine that gives the error. On the problem machine, my profile and "My Documents" folder is mapped by our administrators to a folder on the server, but TBB is installed on the local machine. I had TBB2.x installed on the problem machine previously (in the same location) and did not have this problem.