I downloaded a movie and endied up with just the sound-no picture. Any ideas why?

Could be due to various things. Such as they didn't encode the sound with the video. Else, you don't have the right codec for the video (perhaps you have an older version even.) Try another player like VLC: CODECs list for Movies

Also when downlding videos, check to see if it's on the Bitzi database. You can find out if it's a good file or not. Bitzi Web Lookup ...