Baffled... Only a few clips in entire session are producing audio

Urgently need help with this mystery of a situation.

My session has 30 something tracks and 10 buses. I was doing some work on 3 select clips, panning and soloing, looping etc., until the session wouldn't play for no apparent reason as though the audio engine had halted. I eventually just rebooted SONAR to get it running again. It worked, but now those 3 clips are the only clips in the entire session that are producing any audio.

Nothing is soloed, exclusively soloed, no channels muted, no clips muted, bussed incorrectly or panned incorrectly. Every channel is the way it was, no outputs have been altered. Other sessions work totally fine. My I/O and relative software is fine and dandy. The channels are still able to carry signal, as I can manually whack a drum machine for example and see the signal coming through the relative channels so the issue seems to be with the clips. Its as though the program is completely unable to read any audio data from all the other clips on the session, the path to the original audio files found in the clip properties are sound and the visual image of the clips show the exact same fat waveforms as before, so the data is still there. Peculiar enough, if I copy the dud clips to a different session, they still don't play.

Whatever I've done I've managed to render my entire session (bar 3 clips or so) totally useless! Nothing seems to be wrong whatsoever bar the fact the clips simply don't play. If anyone has any ideas of something I may have missed or something I have done, or a rough idea of where to look from here I would be eternally grateful. Even tried a system reboot to no avail, I'm incredibly behind schedule and ready to tear off my own head. This is torture! 

Thanks in advance for any help offered. 

McCanno,
   Some long shots. (1) If your project is set up to store the audio in the project's own folder, look in the audio folder of the project folder.  Find the wav file for a failing clip and see if it'll open in an audio editor, and if it has audio.  If so, try saving it to another file (from your editor) and import (File - Import Audio) that file into your project. (2) See if the clips will export (File - Export Audio).  If they will, and have the audio in them, then reimport them. There's a similar export you can do if you double-click the clip to open it in a Sonar audio clip editor. Then click the "Save Loop to wave file," and see if that has your audio.  (3) If you can shell the clips to an external audio editor (I can't get Sonar to shell out to Sound Forge or Cool Edit any more -- it used to be Tools - Cool Edit, or Tools - Sound Forge), see if you get any audio there.  If so, save, then import the saved file. Who knows?  Earl