Just to add some information, I've now tried to run the live CD of Natty Alpha 3 on my problem computer. It reverted to standard Gnome in stead of using Unity, and it was just as flaky as Maverick. Noteworthy, Natty Alpha 3 Live ran smoothly, with Unity, on my Sony Vaio laptop with AMD processor and ATI graphics.
Just to add some information, I've now tried to run the live CD of Natty Alpha 3 on my problem computer. It reverted to standard Gnome in stead of using Unity, and it was just as flaky as Maverick. Noteworthy, Natty Alpha 3 Live ran smoothly, with Unity, on my Sony Vaio laptop with AMD processor and ATI graphics.