I just had a similar type of error occur in my environment. In my case it was due to a WrongModeException that I saw in the logs. I had changed one of my properties so it was no longer valid. You can check the PegaRULES log to see if there is more information there. You could also check the section for errors, maybe try with an empty section and then add pieces back in if you don't see anything helpful in the log.