Mac mini / Yamaha Mixer - No Sound

I have a Yamaha MW10 mixer connected to a Mac mini via USB support. Playing a Yamaha keyboard PSR 403 connected to the mixer there is no sound heard from the MAC's internal speakers although I can notice for a signal level change in the Cubase LE S/W and in the Mixer. What is wrong?

Thanks, drorbn2000.

couple different things could be the problem... In most DAW programs if you don't arm the track for recording you won't get any sound.
The only other thing I can think of is that you don't have "Built in Output" selected in your Audio preferences.
You could also try selecting the MW10 as your output and connecting your speakers to it. This will probably give you better quality sound. I don't know though because USB isn't an ideal audio interface.