Topic: some noises on my monitors

I used RME fireface 400 since a couple of month by using Win XP. It was all very fine. Now I changed on Win 7 on a new computer and I get some strange noises like humming frequenzes of a radio.
I used the output 5+6 for my yamaha HS 50M with symetric jack cable.
I switched off the internal audio card,but nothing changed.
So what can I do ? Please help.

Intel I7 2600 K, 8 GB RAM, Cubase 5, RME Fireface 400, RME Quadmic, Focusrite Octopre LE ADAT