Error opening my file in Mplayer

Hi All,
A fatal error appears in screen when playing movie in MPlayer. I’m not sure if I forgot something to be added in mplayer. I installed mplayer in Ubuntu 7.04 64 bits. I can play the mplayer in my other unit using Fedora. Is there something wrong with my video in Ubuntu? Any ideas? Thanks in advance.
Fatal error:

Fatal error!
Error opening/initializing the selected video_out (-vo) device.
OK
