vidalia.conf doesn't say what version of vidalia wrote it
Tor's state file says
TorVersion Tor 0.2.3.12-alpha-dev (git-184a4552930d4f13)
I notice there isn't anything like that in Vidalia's config file.
If there were a version in there, then we'd have more options on how to handle backwards compatibility when solving issues like #5122 (closed).