Re: Getting GLX to work ...
well, first thing i could see is, that you load the GLCore module in X. Comment it out in XFree86Config-4 file and try again, I don't know, if that's related to your problem, but as can also be seen in the README of the nvidia-driver, one shouldn't load the GLCore module together with the nvidia driver.
ohh, I see youre not explicitly loading GLcore in your config-file, anyways it gets loaded by the Xfree-supplied glx module. Seems that your nvidia-glx package didn't install right.