I seem to remember this happening before, and you fixing it, but perhaps not.
Anyway, the problem occurs when using the cursor keys to move to another film, shortly after changing a status of the current film (taking off a rating, or changing a tag, etc.). It's most obvious when changing several films one after the other; make the change with the mouse, tap the down arrow to the next film, make the change, tap the arrow.
If the gap between changing and pressing the down arrow is too small, then it just starts scrolling down film after film to the end of the list (as if the arrow were being continually pressed), then locks up (and has to be ended with the task manager).
Other than that, tags are great, and I'm enjoying being able to play the prediction game
, so ty