Profile a running Vidalia
Look at vidalia in oprofile, and let us know where it spends its time. In particular, there are some pieces of the code that seem to take a lot of energy (e.g. all the country code lookups for the new network map).
There are many reports recently of Vidalia freezes, and it's possible some of them are just Vidalia being slow and not being responsible to its UI while it's being slow.