Cubase 6 and RME FF800 with external FX


I just updated to Cubase 6 last week and everything was working fine until now. I’m used to mix with my FF800 and some external compressors. Before I was working with CB 5 everything was great, no delay or anything like that. Now when I send a signal though a mono bus to the compressor I get the returned signal in the center and another signal either left or right depending on the output I use in the RME interface. When I mute the main output in Cubase I still hear the panned signal.
It seems like the FF800 it’s in some sort of direct out and linking both outputs (i.e. 7 and 8), also because I get input signals in both of my mono compressors even though I’m just sending it to one (i.e output 7). I tried lots of things in the Fireface mixer but with no results. I hope someone got the same problem and can help me solved. I need to start mixing! Thanks!