Can't connect to database

Dovecot has been giving me problems for the past week or so. Today the error log showed me this:

Jan 2 13:33:39 grace dovecot: auth-worker(3250): Error: mysql(localhost): Connect failed to database (postfix): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

• waiting for 5 seconds before retry

The socket is there, showing full permissions (rwx for owner, group, and rest of the universe) so I can't understand why dovecot can't connect.

Is there anyone who can help?

Ken