I had been running the older version of the toontown launcher on Vista without problems. My Sister told me about the new version of the launcher, so I deleted ToonTown and installed the new launcher and now I have the same problem. I reported it as a bug and just received the following message from support:
Dear Toontown Guest,
Thank you for your bug report.
We are currently looking into your problem. All players will receive
this fix in an upcoming patch that will be automatically downloaded and
installed when released.
We appreciate your help and patience in resolving this problem and hope
you will enjoy your time spent in Toontown.
Thank You,
Kanji
Disney's Toontown Online Member Services