Obviously, my fault...
I tried to compile GtkGLExt, and then tried to apt-get it. Solution was easy though, I just made a "make uninstall" first and then reinstalled it via apt-get.
Now works like a charm and with the menu, which I find it's a huge plus.
Regarding the graphics chip, it's a Intel 830M. Not the brightest one, but still enough for running the Linux Mint 9 Gnome desktop and XRoar at nice speed.
Thank you very much for your help!