If Tor leaves behind its port.conf file, Vidalia and Tor race at next startup

If your Tor dies in an unclean way, its port.conf file stays around. Then the next time you run TBB, Vidalia says "is there a port.conf file? Why yes there is", and then reads it and uses the wrong ports.

Some users, e.g. on OS X, have reported this happening in practice.

Sometimes it works, since Tor writes a new one before Vidalia checks.