First of all, I loved this plugin. You have no idea how much time have I lost by not having a undo menu.
And now that I have I would like to help you out. Just a problem that I noticed. I'm on Windows XP SP2, and if it helps I have brazilian regional settings (but the Windows XP itself is in English).
And this picture pretty much explains the problem:
I've done a few extra testing and the situation is that those characters appears in that order and after that the date is blank, but only for dragging operations.
Oh, and, do you need the miliseconds? It looks a little too complicated with all that numbers when all you want is to know is how old is that change.