Help me please!

My setup is vocal/ guitar into mixer (Yamaha MG 10/2) into computer (Audiophile 2496), then back into mixer then to monitors.

I know this is possible as I had this setup working before - but I can't for the life of me figure out how to do this now - I keep getting the signal from the computer looping back into the computer - whereas I need this signal to be separate

- does anyone have this mixer I know its pretty popular? or perhaps someone who has a better understanding of recording could help me sort this mess out?

here's a link to a picture of the mixer:

http://upload.wikimedia.org/wikipedi...maha_mg102.jpg

Please someone help me!

thanks

Dave