I've been trying a few things myself ..
I also have your WMP plugin and your freeware AVI splitter, and using the same file, both of those save and play beautifully in Media Player. Also what is strange, is that I can make a couple of random cuts in the video splitter, and save, and (most of the time) it saves and plays, but when I make three or four cuts, to edit out adverts, we're back to the blank screen again.