Tracks load but some tracks are empty

Bulid# 1756

This is not a major issue for me as I have multiple versions of the related project and fortuneately some of them do load correctly. For example I have a song with 6 tracks. I apply all the necessary EQ and effects and then save the song. I then reload the song and create a whole different set of editing parameters. I then save that version with a different name i.e. song ver01, song ver02 and so on. Let me also state that the related .sng files have been created with earlier build #'s. I was doing some clean up and review of all my projects when I encountered the problem. I load ver01 of the song and all six tracks load without any error message. Four of the six tracks display a wave file in the time line and play back. The two remaining tracks appear to contain all the EQ and effects but the timeline wave is blank and do not play back. This is not a .npk file issue as the tracks do not play back. When I review the song information the path to the missing .wav is correct and the wave file does exist in the named directory. If I insert the suspect .wav file as a new track it plays back and displays correctly. If I load another version of the same song all tracks appear and play back without a problem. I review the song information and the path to the .wav files are correct just as they are in the version that does load corrrectly. Weird eh? As a final test I renamed the suspect .wav files and as it should n-track immediately reports that it cannot find the files. The simple work around would be to just to reinsert the .wav files back into the song and copy all the editing parameters to the new tracks and then remove the problem tracks but that would be a pain.

Any thoughts, comments or suggestions would be appreciated.