Hi, u could download realone play for linux and install it. if you don't like it, no problem, you can use xine to play RM just identify the code' path to xine. Now, restart your xine again and see what happy, Good luck!
BTW: i dont like mplayer, for i never suceseed installing it on my computer. and to me, xine is enough. i can use xine play anything on my computer.. but there is s little problem, if i use xine to play rm files, when it is close to end,,xine seems to be crashed, i don't know know why.