Before I post this to Bugzilla as a bug, I just want to find out whether I'm doing something really stupid.
I ran Firebug against it and it shows both an IMGatewayListRequest and IMGetRosterRequest SOAP call being done the first time the IM tab is clicked on. Nothing is sent the second time.
I can't find any obvious errors in either mailbox.log or zmmailboxd.out
Anything I'm missing?