Ghost emails in Snow Leopard (10.6.8) Mail


I'm experiencing two email oddities with my recently installed Snow Leopard:

1. "Mail Activity" consistently announces the arrival of twice the actual number of incoming emails; eg, 10 when there are only 5.

I do have two registered email addresses, but then so I did before with Leopard, but without this hiccough.

2. "Mail Activity" announces from time to time the arrival of emails when none appear in any of the mailboxes; eg, the Inbox, Junk, or whatever.

It seems to coincide sometimes with me transferring emails from one mailbox to another.

In both cases 1 & 2, I've tried rebuilding the mailboxes in question, but to no avail.