Mismatched stereo track volumes

In the past several months, I have been having a problem whenever I record using my computer.  The left stereo track's volume is always considerably higher than the right one, regardless of what I have plugged in to the computer.  I have tried changing the internal recording volume for the soundcard, and while this does seem to change the ratio of the volumes, the problem still exists.

I was wondering if anyone else had encountered this, and might know if there is a way to fix it.  At the moment, I suspect I just need a new sound card.  I've been fudging it so far by playing with the track pan, but it sounds nowhere near as good as a stereo sound that was clean to start with.  I'm pretty new to all this, so it may be that I am just not experienced enough to get a good sound out of it that way.

The recording software I'm using is Cakewalk's Music Creator 3.

Thanks. I hope someone can help.  I tried to find a thread where someone had a similar problem but haven't come up with anything.

Yes, anything played through the CD-rom sounds fine.  Actually playback seems okay in general - the volume shown in the Cakewalk software is definitely unbalanced right in the recording itself.  I have old recordings where the tracks in the software have even volumes, and they play back sounding right.  I have not tried uninstalling/reinstalling the soundcard drivers, that's a good idea.  I did give it a try with the recording software and the mixer software (at first I thought the mixer I bought a few months ago was the source of the problem, until I tried recording direct to the computer again and still encountered it).

Because this problem showed up shortly after I bought the mixer, it might also be possible that there's some software incompatibility going on, independent of whether I'm actually recording through the mixer or not, since the software is still installed even if I'm not using it.

Wow that was a long sentence....

Which is the record i/p that is causing the problem?