Had same error on 6.5 CPPM, and found that it was due to a Firewall block for an authorization source.
Once we allowed traffic from CPPM node to authorization source (external SQL db), we were able to avoid the error.
I've seen this anytime you enable an authorization source and the query fails. I'd like to make some authorization sources "optional" so that I can have other logic to handle when authorization sources are unavailable.
Guess it's time for an RFE....