Might not be the server itself providing the message, but the load-balancing component and/or front-end.....but that's just supposition on my part as I have no details as to the current hosting setup.
It could be - but the reason I discounted that is there were no status values alongside it - even if they were meaningless to the laymen the basic rule of programming is to put a unique value against any unforseen/half expected exceptions to identify where the exception was caught.
What I think is more likely is the php library requesting access to the databases has a default throw of an exception with a crude message and this is what is being seen.
You may be right - but I would not put much behind any vendor that does not associate a result code against any error - even if its unkown and to be honest in my experience the guys who run the board know not to dabble in the unknown too.