I ran into this issue and I solved it by removing existing xserver- driver-xorg (which caused DRI fail to load) and removing fglrx kernel module from running kernel (which seemed to prevent GLX_EXT_texture_from_pixmap from loading).
-- desktop-effects doesn't start compiz correctly https://launchpad.net/bugs/80734 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
