I have found that the issue is a corrupt item in the mailbox. To fix it, I open outlook, do an Advanced find and open the top one. I then hit Ctrl+> (or<, forget) till I get to a point that I get an error that says "Can't open item" or similar. I delete that one and the errors in the log go away. I do not always get an error like the above though and it is a fishing game. It would be nice if RIM put the subject in there so I could find it easily and delete it.
I agree, very annoying as it is the only predominate log entry I have. Got rid of most of the others ones through the years....