Which RAM to solve my problem?

Hi guys

I got an ASUS P5Q Deluxe, E8500, HIS HD4850, and want to get some new RAM! - currently have 2gig Corsair XMS2
Was looking at 4GIG upgrade kit - Corsair again? XMS2 still good? MHz? OC?

What you other ASUS guys running?

I need to replace my current RAM as i think its broken
PC randomly freezes while Windows has finished starting up, or im listening to music, or browsing..etc

What i have also noticed only a few times, is that while running games or some programs, it stutters, as if it was about to freeze (sound stutters and screen freezes for the short time) then all resumes fine.
However only once has it completely frozen on my while playing games.. sound loops/stutters and screen frozen (as you would have guessed no doubt

I tried to run some RAM diagnostics and they were all "fine" - im not convinced.
My RAM timings are on Auto on the MB - they are correctly defaulted!

Any suggestions/recommendations?

Thanks !

The Kid

a pleasure you entertain you.. !
its what happens when bored at work..

but seriously though, which RAM you recommend?
and by any chance anyone had the same freezing problem and resolved it?