SSE Optimized Audio DSP Library Error on startup

This is doing my brain in!!! I installed/activated/registered Cubase Ess 5.1.1 successfully. but every time I try to run the program I get this message and Cubase stops working. This is the first Cubase installed on my computer. I have been all over the web with no success and Steinberg support gave me an option on Friday but it didnt work (APP DATA) and I now have to wait till Monday to try them again. HELP!!!