By default, if you don't highlight what you want to be bounced, Cakewalk and Sonar will bounce all they think is there. If you happen to have a midi note, a clip of audio, an automation, or some sort of data several seconds, minutes, (or even hours) after the end of you track, it will keep chugging along until it thinks it is finished. This is simple to fix- highlight only the section that applies to your project and go to mixdown audio.