It's a pretty common problem, actually. What you need to do is disable the local cache mode so that you can fix the MAPI settings. Once you've done that you want to delete the duplicate messaging subsystem registry key. The easiest way to do this is to do a Start/Run and then type REGEDIT. Get rid of everything under HKEY Local Machine - that's the stuff that's screwing you up. Reboot.
Normally I charge for this sort of service but for a great guy like you it's on the house. Happy RamaHanuKwanzmas!