Mplayer won't play full-screen video running Rhythmbox

[Alessandro]

Mplayer works fine untill i play a song with rhythmbox. After that mplayer works, but it cannot play full-screen video. If i want to wacht a file in full-screen mode i've to close rhythmbox.

My /.mplayer/config file is empty. I don't use special options for it. I've this problem since 6 weeks. Till 6 weeks ago i was able to watch files in full-screen mode also running parallel Rhythmbox

I report following the error lines.

This is a part of the console output, that i receive when mplayer works with full-screen mode:

==========================================================================
open: No such file or directory
Couldn't open: /dev/mga_vid
open: No such file or directory
Couldn't open: /dev/mga_vid
[VO_TDFXFB] This driver only supports the 3Dfx Banshee, Voodoo3 and Voodoo 5.
[VO_3DFX] Unable to open /dev/3dfx.
==========================================================================

This is a part of the console output, that i receive when mplayer doesn't works with full-screen mode:

==========================================================================
open: No such file or directory
Couldn't open: /dev/mga_vid
open: No such file or directory
Couldn't open: /dev/mga_vid
[VO_TDFXFB] This driver only supports the 3Dfx Banshee, Voodoo3 and Voodoo 5.
[VO_3DFX] Unable to open /dev/3dfx.
Xv: could not grab port 65
Could not find free Xvideo port - maybe another process is already using it.
Close all video applications, and try again. If that does not help,
see 'mplayer -vo help' for other (non-xv) video out drivers.
==========================================================================

Is it a bug or just an error of my pc?