Hey mate,
I use SDK 2.1, drivers 11.12, I installed the SDK via the WinRAR method of extracting and installing only the .MSI file.
Now I'm clocked at 1000 MHz / 350 MHz, and get 375 mhash/s per core.
375 mhash for 1000mhz on a 5970/5870 core is REALLY slow. Just saying.
You should easily clear 460 mhash at 1000 core speed for a cypress xt core.