Audio trouble! (there was no audio forum...)

[JagrAssist]

I have a cord plugged into my headphone jack and into the back of my receiver. This has worked for years, but recentely I only get music out of my right speakers and not the left speakers. I thought at first that my speakers were blown, but I realized that when I play the radio or CD's off of my 6-disc changer all of the speakers work just fine. So the problem seems to lie within the computer when I play music off of it (it's the same problem on all media-playing programs). What's going on and how do I fix it?! Thanks!