I had a problem with a friends new Vista machine yesterday. When trying to check email via Tor the connection failed instantly, not like the normal time out messages you get from time to time. Firefox was working fine though.
The way I managed to 'fix' it, eventually, is by uninstalling Tor button and manually input the proxy setting, but instead of 'localhost' I had to use '127.0.0.1'. The only possible reason I could find for this was that in the command line 'localhost' resolves to the IPV6 address :::1 instead of the IPV4 address 127.0.0.1, I am not 100% sure if this is the problem, but if anyone could shine some light on it, please let me know.