Yes to the first two points.
AC Utilities shows a connection error. SQL Interface error - 25. Connection string is not valid
Alright, then there is an issue with the DB connection.
There are two XML files in the AC directory that have connection settings, and dealing with those can sometimes be illuminating.
A short-cut is to use AC utilities to "Reset database connection" or similar. On the road, so don't have it in front of me.
This should prompt you to browse to the database.