Originally Posted by malcolm
This is probably your ATI card, if you have the option try using an nVidia card and see if it fixes the issue. I don't ever recommend using ATI with Maya, although when I bought my Dell I could only get it with a high end ATI so I'm in the same boat as you. I am finding Maya 2011/2012 to be slow in general for doing lots of things. Seems like since they updated the UI to run on the GPU it's kind of crap, like I said tough I'm on an ATI so I have no comparison on nVidia yet.
Having recently-ish moved from an ati HD4850 to a nvidia 460gti (which apparently has terrible GL performance), I noticed little change in general performance, but not with selections. The latest driver updates did help a lot, particularly when moving the camera. Marking menus are MUCH more responsive on this card than my previous, I used to need to slow down my mouses' USB poll rate to get around that a little.
Scruples, I'd suggest disabling the Aero desktop and see how that works for you. If you have a large history on a mesh you're trying to UV, clear it if you haven't already. Is it only selections that lag out, or does moving the components behave slowly too? If you're running any background apps for universal hotkeys, capture, skype, etc might want to try shutting those down for a test.