"Xgl is an X server architecture layered on top of OpenGL. It is at an early stage in development and a number of important pieces are still missing. Xglx is the only server currently available that uses this architecture. It requires an already existing X server, and is only intended for testing and development."
Thus, probably an early erroneous meta-package got xserver-xgl installed? An new meta-package should be released to remove this server which seams to be causing problems to many and which is not ready for prime time use anyhow.
Quoting http:// freedesktop. org/wiki/ Software/ Xgl
"Xgl is an X server architecture layered on top of OpenGL. It is at an early stage in development and a number of important pieces are still missing. Xglx is the only server currently available that uses this architecture. It requires an already existing X server, and is only intended for testing and development."
Thus, probably an early erroneous meta-package got xserver-xgl installed? An new meta-package should be released to remove this server which seams to be causing problems to many and which is not ready for prime time use anyhow.