I'm getting warning in Vidalia running bitcoin through Tor:

Your application (using socks4 to port 8333) is giving Tor only an IP address. Applications that do DNS resolves themselves may leak information. Consider using Socks4A (e.g. via privoxy or socat) instead. For more information, please see http://wiki.noreply.org/noreply/TheOnionRouter/TorFAQ#SOCKSAndDNS.

From a brief chat in #Tor on irc.oftc.net:

You can modify your socks code to connect to a hostname
(you can use an IP address as hostname without any trouble, if you're using socks5)
or you can use socks4a and stuff will also just work

I don't know nuthin about SOCKS, but I'm hoping somebody else does and can fix this...