I just submitted an email to support with a copy of my backup and performance in question.
Essentially, I was doing some volume balancing between two performances of M. Britt profiles. I had been jamming on the reference performance and all 5 slots with no issues prior to realizing there was a volume difference between the two. After successfully adjusting the performance that needed adjustment, I went back to the reference performance and the rig in Slot 5 now will not play any sound at all. I checked every setting I could think of even though I had adjusted NOTHING on that rig.
This is disturbing to say the least - its the second performance-related issue I have had in a month on both the 5.0 beta and release. I have not received any response regarding the first issue either. Stay tuned.