How did you try to log in? I generally use command line for database backups, so you might give the following a try after logging into a DreamHost machine via SSH or Telnet:
/usr/bin/mysqldump --all-databases -hsanspoof.dreamhost.com -uDBUSER -p > ~/db.sql
If all else fails, contact support, though it may be several days before you hear back since it’s Christmas weekend. Maybe someone else in the forums has an idea.