Ok, I have 4 computers all running Ubuntu 12.04 with Gnome Shell. on all computers when ever I play games in wine I set wine to run in a virtual desktop. On the first 3 computers I can use things like "Alt-Tab" and I can use the "Super/Windows" key to get into overview mode while playing games and it functions absolutely flawless, I can even move the game to another deaktop and continue playing. However on the 4th Computer neither "Alt-Tab" or "Super" Do anything, as a matter of fact if I hit them more than once the window will loose focus and I have to shutdown to get out of the game. I also noticed on the 4th computer that the Volume popup for Gnome Shell doesnt diplay either, but it does on the other 3.

All 4 Computers are running Ubuntu 12.04 (fully up-to-date), and they are all running Gnome Shell (Fully up-to-date from the offical Gnome 3 PPA). All Computers have thier respective proriatary graphics drivers installed.

1st: Works Fine
AMD CPU and
AMD Radeon HD6850 Graphics

2nd: Works Fine
AMD CPU (mobile) and
AMD Radeon HD 6520G graphics

3rd: Works Fine (Only PC running 32bit Ubuntu)
AMD CPU and
Nvidia GeForce GTS 250 graphics

4th: Doesnt Work
AMD CPU and
ATI Radeon HD4850 graphics

EDIT: A friend of mine is also running 12.04 64bit with Gnome shell and a Radeon HD 4850, he is also not able to do this either. Could it be something specific to the HD4850? I can do it just fine on my HD 6850.