It would be very nice if you could send me a short answer to my question. I hope you find it interesting. I assume this error is due to the fact that the move event is supposed to return an AEList of all the files which were moved, which in this case is too long. I would call that a bug, because a script shouldn't stop because the result is not available unless you are actually trying to use the result. I was expecting a fast, hard crash.
Finder relaunches itself automatically, and everything works just fine.
The script, of course never got executed. Kudos to all responsible for letting us force-quit the finder and survive like that. Mac when it does things like that. That's an interesting script notion though. I was trying a manual conversion of my handlers from HyperTalk to AppleScript, but hit a wall because of some missing AppleScript commands in HyperCard.