Comment 12 for bug 138933

I guess I wasn't clear enough in my last message. I already solved my problem - sorry about that.

The problem was three fold:
1. The hidden .nvidia* file: causing the nvidia driver not to load because it thought it had the wrong version. Removing the file fixed the problem.
2. XGL: was conflicting with AIGLX and direct rendering. Removing all XGL packages fix the problem.
3. Xorg.conf: was improperly configured (most likely configured for XGL), and was probably causing GL problems.

What I was trying to say is that many people will probably have the same or similar problems upgrading from Fiesty to Gusty. If they had installed XGL (like I did to try out Beryl), then it will conflict with Gusty's AIGLX and there will be no 3D acceleration. Also if they have a Nvidia card, then the hidden .nvidia file could cause problems with loading the correct driver.

The update-manager or the nvidia-glx* packages or some other script should fix the hidden .nvidia problem.
Also a message should be shown if the user had installed XGL; informing them that it will conflict with AIGLX and is no longer necessary and should be removed.

Other than that you can close this bug. It's more turned into a suggestion of how to stop this problem from happening to others that upgrade.