Can't open this item. The object could not be found
 

I am running Outlook 2003 (SP2) on a Windows XP (Sp2) machine. I am
constantly getting the error message "Can't open this item. The object could
not be found" when I try to open messages with attachments (tif) from my
inbox. After clicking on OK (from the error message screen) I am able to open
the attachment. The issue repeats itself on the next attachment ..and so on.

In addition after accepting a calendar request, I am unable to open the item
with the same error message being displayed (Can't open this item. The object
could not be found). However, this time the request never opens.

I have tried the following:
- deleted / recreated outlook profile
- Updated to latest hotfixes and SP's
- Detect and Repair
- Cleared Form Cache
- Unistalled and reinstalled
The only thing that works is working on another machine on Outlook 2000.

Any help would be greatly appreciated.