This is actually something that @nokiacareus is working on with me on Twitter... I found that if I had notification sounds off, my music played fine... As soon as I brought the notifications to an audible level, the first one I would get would make Nokia Music, SoundTracker and every other music App (except Slacker?) drop sound. Exiting the App and starting it over helped temporarily, but I was back to skipping tracks as soon as the next email, text or phone call came in...
@nokiacareus replied to me with the following: "This is something we are currently investigating. We'll share this with our team and let you know when we have an update."
I found by silencing all incoming sounds while using Nokia Music and the others that the issue didn't happen. But everything must be turned off for this to work. It's ok for me since I usually only use it while working out, but it could be frustrating if you wanted to stream at your desk and still know you had a phone call without staring at the screen.