On May 24, around 1800 GMT, encountered what appears to be same issue (displayed a page headlined "database error" and stated "The PPRuNe Forums database has encountered a problem").
A check using
https://downforeveryoneorjustme.com/ indicated the site appeared to be down.
Happened again at midnight GMT on May 28-29, 2018. Given the hour, wasn't sure if site undergoing planned maintenance, or ??? I didn't try again until hours later, so can't speak to duration of the most recent apparent outage. Site administrators almost certainly aware of issue, so this is simply for benefit of anyone else who encountered that error message. It isn't just you.