First off, congrats on your new monitor :thumbup:
First thing that comes to mind with me is reinstalling your drivers again too, only this time I'd like you too use
this program. It dletes all files that aren't standrad removed by the Nvidia uninstaller itself. Let me know if it works, there are numerous things that could cause your problems so I'm just taking my first guess here,. don't give up if it doesn't work.
Also download the trialversion of
this program to delete any errors in your registry, defrag your harddrive and more. It never hurts and might just fix the problem.
Your psu is powerfull enough
Edit: seems mr. Numberman beat me too it

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Kamisorix has the sex appeal of a NXS
PSN name: Gazz1979 (feel free to add me)
Currently playing: Battlefield 1943 (PS3), Battlefield 2 (PC) and Wipeout pure (PSP)