I'm using Sonar 8.5 Producer with Win 7 x64.  When I play back my multi-track projects within Sonar, it sounds perfect.  But when I export the final project down to a single file, the final audio has occasional drops in the volume levels.  Every few seconds there are slight drops, not 100% dropouts, but enough to make it noticeable.  Basically, the volume goes slightly up and down throughout the entire song.  I've exported to wave and flac and tried many different export settings, and tried playing the audio back on different programs and systems.  Same result.  Please advise.

If you have any 3rd party plug ins look for a demo , often they add this to demos to make you fork over the cash.