Thunderbird (using IMAP) is freaking out for me. It keeps seeing hundreds of 'new' messages in my various inboxes, which are actually the messages that were already there. Then any time I click around, when it contacts the server to see if there are new messages, it's about even odds that all the messages will disappear and then the headers will be re-downloaded.
Irritating, as I'm getting 'firstname.lastname@example.org has 200 new messages' notifications about every 2 minutes.
Also, the Panel seems hosed.