Trouble recording from my stereo to CD-R

This is a follow-up to a previous question. I have a wire going from the headphone jack of my stereo to my line in jack on my computer. I record albums and cassettes in .WAV files and transfer them to CD-R, but when I play them on a CD player I only get music out of the left side speakers.

If I put the CD in a computer, though, I get sound out of both speakers. What’s going on?