is it a mixer prob ? plug your phones or monitors into your outs that are going to the pc and see if the fault is the mixer or the pc.

if its the mixer - has it got group outs , have you routed to a different buss and got the eq weird on the buss

in soundforge are u using the propper soundcard drivers or are u using the emulated ones ? if its the emulated drivers are u sharing it with another app?

have u got a webcam or mic plugged in that soundforge could be recording from , ie - your hearing it ok thru the speakers from the mixer - but is that sound going into a usb cam mic and recording from that etc.

have you played your music really loud and blew your ear drums up ?
when was the last time u stuck cotten wool proddy thingies in your ear? :D

hope tjis helps . if not try reinstalling soundforge