You don't say 'which' drivers you use (I'm presuming the 169.25s as they are the latest whql).. But as you mentioned Crysis, try the 169.44s as they were written for Crysis 1.2 (patched version). You could also try different drivers to the above if the ones mentioned don't fix the problem. Here's a page of drivers for vista:
download from Guru3D.com

I'm currently using the 174.44 betas as they're stable and very fast...

You also mention temps aren't a problem but only gave your chip figures. With a chip over 3GHz your Northbridge is going to be pretty warm too (very warm in fact). Usually they're rated to go pretty high but just check it out if you can. A utility like speedfan or sandra will help you to obtain the temps.
You could also try replacing the sound drivers to ones modified by 'Daniel' See here:
http://winvistaforums.com/windows-vi...ers-vista.html

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