A few days ago a disc in the server gave up, it only gave back reading errors.
The last DB backup was 20h old, so not much lost probably, but they can't contact anyone at the data-centre, where the server is hosted, and they don't have any physical access to it, so a bit of patience is needed.

There is a thread in the project forum about it (forum is hosted on a different server), but it's currently mainly in German: Server Error: Can't attach shared memory

Yoyo is back online, all seems to be running fine.