I tested Matin's suggestion. The fallback works properly if /etc/X11/xorg.conf is simply not present.
I moved the nvidia-current.ko aside, restarted. The X.org.0 shows that the order of preference for the autoconfigured drivers is: 0: nvidia 1: nouveau 2: nv 3: vesa 4: fbdev. In this case, nouveau is chosen. Metacity starts. Jockey ('Additional Drivers') shows that Nvidia is "activated and currently in use", even though lsmod, Xorg.0.log and glxinfo concur that it is not in use. I restored the nvidia driver file. I was tried to switch drivers by logging out and in, but nouveau was still used. Then I restarted gdm, but nouveau was still used. I didn't try rmmod and modprobe. After rebooting, however, nvidia was used again as the preferred default. The only (minor) disadvantage is that the nVidia splash screen displays (for <1 second) when it loads, because the 'Option "NoLogo" "True"' is no longer being read from the non-existant xorg.conf This is with Natty Daily 2011-03-18 Linux 2.6.38.7.21 nvidia-current 270.30-0ubuntu3 xorg 1:7.6~3ubuntu11 amd64/mac GeForce GT 330M -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/522061 Title: Nvidia proprietary drivers fallback test failed -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs