Such an annoying problem, especially for connecting to GMail via IMAP.  I constantly get the error: Too many simultaneous connections.  The worst part is this has been known ever since Leopard shipped:

http://discussions.apple.com/message.jspa?messageID=5820548

http://discussions.apple.com/thread.jspa?threadID=1207290&tstart=30

Any fix, Apple?

UPDATE

This problem seems to date much further back then Leopard.  I’ve found references to this same issue in late 2003 (v10.3!!), here:

http://www.macosxhints.com/article.php?story=20031130150826388

Unfortunately, I don’t have access to server configuration as my problem is with GMail.  It seems like Apple may never fix this…