I have many, many project in Sonar.  I recently tried to open one to do some work on it.  When I open it, the timeline is "empty"  The tracks  I/O's are there but no actual .wav files containing the recorded instruments/automation etc...  When I navigate in windows explorer to the actual folder of the project, all the files are there.  I'm relieved that they are still there and haven't been deleted somehow, but why are they not showing up how they're supposed to in Sonar?
How do I fix this? 
 
Thanks,
Eric.

Is this midi or audio or both?? 
 
If it's just audio you can drag the wave files from the audio folder.
 
If it was midi then that is imbeded in the CWP file so you hooped..
 
Is there any little dots in the tracks? THat tells you there is data further along. 

Are the tracks actually empty, or are there empty clips on them, without waveform images?
If you're not getting messages of missing audio, I suppose you have the clips on the tracks?
Did you audition the tracks - hear anything? The waveform image creation is a separate thing, the images are not needed to hear the audio.
In case it's just a visual issue (empty clips), emptying the Picture Cache folder makes SONAR redraw the waveform images.
IIRC there is a separate command "Redraw images", too.