[Dovecot] Expire plugin does not work

Hello,

I followed the instructions on http://wiki2.dovecot.org/Plugins/Expire to configure the expire plugin, but when I move a message to the Trash folder, I get the following error messages in my logfile:

dovecot: dict: Error: sqlite: exec(INSERT INTO expires (expire_stamp,username,mailbox) VALUES ('1292525469','christoph','Trash')) failed: unable to open database file (14)

dovecot: dict: Error: sql dict: commit failed:

I have attached a "dovecot -n"-generated dovecot.conf, the configuration file for the expire dict service, and my sqlite3 database file. In my filesystem, dovecot-dict.sqlite currently has permissions 666.

Regards Christoph