I had this yesterday, and assumed there was some sort of maintenance going on, assuming it's not a ddos of sorts.
There is a simple trick to know when the forum is working or not... simply go to the main page where you see all the boards. Press F5 a couple of times. If nothing is moving (if there are no new posts) then come back later because when you post you will still keep getting the database error.
I think this issue was solved..the link given by the op i made a posted and didn't received the database error.
Maybe like you said maintenance because i was remember that some of my post was gone or i think their deleting the oldest thread.
Well the site right now looks fine..