Intel i2500k (not oc)
8 Gig DDR3 Corsair
Asus GTX580 DirectCUII 1.5 Gig
850 Watt Corsair
Windows 7 64 Bit
OS on Intel SSD 320 40 GB
Steam on WD Caviar Black 1 TB
Dell Ultrasharp 2412M at 1920x1200

So last Saturday I deleted the Nvidia beta drivers and installed the old Asus ones that accompanied my card and bam everything worked at 50-60 FPS
Today I wanted to continue the game and framedrops to 9 FPS reappeared.

This is doing my head in GRRR