I guess just make sure that the line-in on your sound card or any other settings doesn't actually have a mute tick on the volume control. Also be sure that you rca cord is inputted into the line in of your soundcard. Usually it's just volume adjustment that's the main cause, or something else little or insignificant.

Thanks for the suggestions Paul...I have already checked my soundcard properties...making sure nothing is muted. I also went into soundforge and made sure the recording device is selected to use my soundcard. Also, the rca is going from my master out on my mixer to the line in on the soundcard. I'm so confused as to why it won't pick it up, seeing as I can hear my records coming out of my pc speakers...?

I had the same problem hey. I just kept fiddling about and it worked eventually. It's normally something just really stupid. Trust me!