>Any real-time AV scanner in operation? Any unusual processes running on the box?

It actually happened on a third box once as well. So out of three boxes two faster ones are running McAffee's VirusScan, and the slower one is running the AVG. What's funny is that the error used to appear few times before, but it was tracked down to a couple of combos attempting to refresh after the tables were closed (during the app's quitting) - that was fixed and hasn't reappeared ever.

This is the only time it happens, during the mass closing of the tables from this dialogue. And it doesn't show any consistency at all. Happens once in a few runs, usually on the first one, and then it takes several runs for it to happen again.