That doesn't sound right! I've used LW for a few years & never had that problem.

Try another video player. Try VLC (which is free & has in-built codecs): http://www.videolan.org/vlc/ (choose the nearest mirror site to you.)

It might also be wise to select one of these mpg files & either make Quicktime or VLC the default to play it. Select one of these files in the finder & press both the Apple & i keys. Go to the 'Open with' section & choose the application you want to open it.