Actually now that you mention it...this was a while ago...I do remember that I also tried just changing the sample rates of all the files in the audio folder, again using Sound Forge, and then opening the Sonar project. Sonar could read most of them okay, but again, with reverse and cut up loops it didn't work. I supposed if I bounced everything to "pure" audio it would be fine, but I wanted to keep the project editable, even with the new sample rate.
I'll have to try again and get a better handle on what does and doesn't work after converting all the files in the audio folder. There may be some simple thing I'm overlooking. Or maybe just bouncing a few strategic files, or changing the position of reversed files, would do the job.