Sorry, I don't have a solution for that. I have no idea why this database is becoming slow. If someone else has a solution it would be welcome.
Two suggestions:
- Make sure that the database doesn't get too big. So truncate ps_connections, ps_guest, etc
- Make sure that this database is the only database in your Mysql installation. The Mysql system tables are not indexed, so if you have more databases in one installation things can become slow quickly.