Music artwork appearing for home videos instead of screenshots

I've just synced my iPhone and it looks like nearly all of my Home Videos now have music album artwork (from music I own) instead of a randomly selected screenshot from a part of each movie. This is a ridiculous problem. Why on earth can't the home movies just be left alone? I have not added any artwork to them as there was no need and I was happy with the random screenshot from each movie which enabled it to be identified easily on sight. It makes no sense that the computer would randomly allocate a music album artwork. How terrible is this software?! Does anyone know how to fix this?