Cubase SX2/RME Fireface 800 HELP

[Cyprus]

Hey guys, I'm not sure if this is the right forum but I recently purchased a Fireface 800 and I'm having all kinds of problems getting it to work in Cubase SX 2 so I was hoping one of you experts might be able to help me out.

I had a Sound Blaster Audigy before and that I replaced with the Fireface 800, everything was working with the Audigy.

If I start a VST like normal and press a key I can see the little blue bar in the bottom right hand corner go up, but no key is pressed on the VST. Also if I manually hit a key in a VST I don't hear any sound.

Also if I use any of the VSTs through their respective standalone programs they work perfectly fine, it's only in Cubase that I'm having problems.

I'm 100% positive it's just a setup issue but I've gone through the manuals of both Cubase and Fireface and I've done tons of trial and error and I can't get it to work.

Any suggestions?