A couple of users over at the Apple discussion boards came up with something that works. Based on what they did, here is what worked for me on several computers:

1. Quit Mail.app
2. Rename the Mail folder at Users/Library to something like MailX
3. Start Mail.app (Appears to rebuild the accounts)
4. Close Mail
5. Restart Mail.app (Appears to re download and sync the directory structure and messages)

ENJOY!

===============UPDATE 10/29/2007 @ 23:15================

Matt Baker of Galaxy Design Pty Ltd reports another possible fix

“I have just deleted the Rules left over from Mail 2.0 and the IMAP is all working.

All of the mail in the folders that were not showing up are there now. Woohoo!!!”

Philip Hayes is Phil is the CEO and a IT Solutions Consultant for Sirius Innovations, LLC. He has been a Mac user since 1990, when he bought his first LC for $2500 (monitor and printer not included). Although he is as proficient in Windows, he hands down prefers working on the Mac. He is currently operating off a Mac G5 tower and travels with a 17" Powerbook. He swears his new iPhone has made him 200% more productive than before.
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