If you get a delay when playing over a recorded track I.e you're playing doesn't line up with what's going on in the inspector, then it's a latency thing, most often the soundcard doesn't support ASIO. You could try new drivers from Creative, but they're notoriously slow on that front.
It's unlikely your disk would be full without you knowing it, so you could try taking some of the load off the soundcard by routeing non Cakewalk functions elsewhere. Otherwise, uninstall & reinstalling the card might do the trick, especially if it was working ok before...