Wellllllllll, I think I found the cause of my bug by accident. I saw that there was an update available for Volume Care, so I went to the developer's forum over on Treocentral to see what was changed. Apparently a bug was found that, guess what, doesn't properly transfer stereo sound to a headset in pTunes after hanging up a call. I updated, and ran into a similar bug in the new release, Volume Care doesn't boost when returning to pTunes after a call, but a quick pause and play resets it. In any event, it looks like I was blaming the wrong app, MagicButton is blameless...
Oh yeah, and I just picked up my Cardo Scala 500. It's charging now, I can't wait to try it out...