[Tenacity]

Since switching to Vista (don't know if Vista had anything to do with it),
the yellow rectangle next to the Undo command always says Can't Undo, even
when I am easily able to undo the action by clicking on the blue curved arrow.

In XP, it helpfully showed the action you were about to undo and only said
Can't Undo when it really had nothing to undo.

Is there a fix for this annoying happenstance? Thanks.