My site's been flaky as hell for the last couple days too. The web server and DB server both respond fine to pings, and the website responds fine, but since Monday morning, when I try to access my phpBB forums, I often get:
phpBB : Critical Error
Could not connect to the database
It comes and goes pretty randomly. It'll work for hours at a time and then fail for hours on end. It was down for over eight hours on Monday. Of course, there's nothing about it on the status page and whenever I send a support ticket about it the response is "Works for us". But it's not just me, because I have users scattered across North America who are having exactly the same problems I have.