File not found: '/mnt/sdb2/movies/Tears of the sun/Tears of the sun1'
This would seem to be the really serious problem.
This is not a codec failure. I routinely get some of the other error messages you posted when mplayer starts, but if it can't find the file you're trying to play, well, it can't play it.
Just for kicks, do a:
ls -al /mnt/sdb2/movies/Tears*
and see if it actually exists? Is it in the directory you thought it was in? Did you type the filename JUST right? Did you mistype it?
Is there is an extension associated with the file (.avi, for example)? From my experience (I just tried it) you MUST give the FULL FILENAME (including any extension) in order for mplayer to play the file.