You didn't describe the cables so I will just assume you're using the wrong kind (mono) instead. Make sure your cables are all stereo.
First thing I noticed about your descripted hook-up is that you have the "cd tape out" hooked up to the mic jack on your computer. That's probably what's wrong as that (typically) is a monorail device (and mono is patched on the left channel.) You should instead connect "cd tape out" to your computer's Line-In jack.
You also need to make sure that you connect both the left and right channels from the computer to the L and R Line-In on the mixer unit (can't tell if it automatically senses a stereo jack on the L channel for 5/6 because the image is a bit fuzzy.)