Must admit I've seen that a few times too (hangs caused by the mpg backgrounds), and I need to alt-f4 out of theatre view and switch back to correct it.
Doesn't seem to matter which video you use either, so my guess is its an MC issue too.
I did notice that it really chokes when you try and use a really high res / large file, but thought I'd hit a sweet spot with my one, but obviously not quite

My new skins are still coming.
I decided to take a different route, as I really wanted personalised content based on the MC library, so i'm coding up an extension to MCWS services to serve up some pretty pictures.
I'd include some screenshots if I could add them directly to this board, but it appears I need to link to them which means a bit of faffing around.
there will be a v1.1 of metrox theatre too, with some fixes (like the on screen keyboard position), and some added eye-candy from your library.