I've just bought a dell vostro 3550 with i7 and AMD Radeon HD 6550M and I've observed that the mouse and the windows flicker (shine unsteadily, sorry my mothertongue is not english).
I've observed this flickering whenever I've tried an ubuntu version with some driver support to enable the 3d acceleration of the video card, i.e. with 10.10, 11.04, 11.10 (all 64 bit).

With ubuntu 10.04 (64 bit) I didn't have that issue but there was no 3d acceleration too.

Do you know of any advice? Which release is better? Should I move to 32 bit?

Notice that when I run under windows 7 the video is working smoothly, so I don't really expect to be an hardware issue.