Windows 7 - Slow Ctrl-ALt-Del, Reaction Slow to switch to menu in games, Slow UAC.

I'm having a strange problem with Windows 7 Home Premium, which I'm hoping some of you can give me advice on.

When I press Ctrl-Alt-Del to bring up the menu where I'm given the option of switching user/logigng off/changing password/starting tast manager, the computer will freeze for about 15 seconds with the display as it is, then it will go black for about 5 seconds, and finally the menu will appear.

If I select task manger, the screen will go black again for a few seconds before task manager appears. Throughout this process, any music playing will continue.

This does not happen If I right-click the task bar and select task manager.

Possible graphics problem?

If the UAC screen comes up, the display will also go black for a second or two before it appears or dissappears.

Within games, GRAW 2(Disk Install) and GTA: San Andreas(Steam), there is about a 20-30(A little less in GRAW 2) second lockout whenever I switch between the game environment and the menu. The actual gameplay is flawless, it's just switching to the menu that causes a problem.

However, I didn't have this problem in Rainbow 6: Vegas 2.


I had a slight problem with ATI Catalyst Control Centre a few weeks back (which may be related), which wouldn't allow it to start if I installed a newer version than Dell supplied. A recent update from Dell solved this, and I now have 10.6 installed. The problem remains, however.

I looked in event manager and didn't see anything related really.

The problems seem to be related, and seem to me to be to do with the graphics card switching between modes or something. I just dont know!

Anyone have any advice, it would be greatly appreciated!
Regards,
Kev

Specs:
Dell XPS
Windows 7 Home Premuim - 64 Bit
Intel Core i7 860
8GB RAM
ATI HD5770 (CCC Version - 10.6)