You need the direct YT-URL of your movie to watch. What you see in Wayfarer or OWB (or any other browser) is an alias-URL, which has to be changed (calculated) to the real URL. The real URL you can copy to MPLAYER, which works perfect.

To find the real URL are 2 (maybe more) ways:

1. In OWB open the movie and look at message window, which schows you the real URL
2. Try to find a online URL converter for YT (afaik are there some...)

At moment I see no way to get converted URL from Wayfarer - maybe there is one, but I don't know....