ok i came to this board through a google search and i think this information is maybe useful:
./configure --with-codecsdir=/usr/local/lib/codecs --enable gui (if you want to use the gui....)
that will work!
so if you get a error with you config file try this:
vi .mplayer/config
and add this entry: vo=x11
so now it works 100%
thx to akshunj for your tutorial about the codecs