With the last version of Junk Matcher, I couldn't get the Bayesian filtering to work so I just left it alone. At the moment, although junk is still filtered as it comes into my InBox, I can't press the 'junk' button - either to mark as junk or deselect the item as junk - without getting the whirling beachball and having to force-quit Mail. I'm not going to scream blue murder, blame Junkmatcher and give it a 1 star rating, but it does seem to be the most likely culprit.