Re: GLX causes Signal 11
Mmmh... From your ls output I gather that you have an unusual setup. ;-) Sorry, I was a bit too quick, I'll take a closer look.
In any case, uninstalling and re-installing won't hurt and it might solve your problem. You do load the wrong extension, even though ls seems to indicate otherwise.
UPDATE: remove /usr/X11R6/lib/modules/extensions/libglx.a or move it to another directory and try running glxgears again. That should probably do it.