Mark, in your case someone must search for your USER_ID in this 3 tables. But first download all PMs if you like to archive them. The easy way is deleting all rows with your ID from this tables. This kill all PMs in your and reciver store. Orphaned PMs will also deleted and the flashing icon should be gone.
The tool function for deleting orphaned PMs in the control panel dosn't fix the problem.
