Spam Assassin User Prefs - Delete Bayes Data problem

[PacMan33]

I am using Spam Assassin User Prefs v1.9 (latest) with RC 2.8.1 on LAMP.

I have activated the option:

$rcmail_config['sauserprefs_bayes_delete_query'] = array(
'DELETE FROM bayes_seen WHERE id IN (SELECT id FROM bayes_vars WHERE username=%u);',
'DELETE FROM bayes_token WHERE id IN (SELECT id FROM bayes_vars WHERE username=%u);',
'DELETE FROM bayes_vars WHERE username=%u;'
);

but when clicking on the "Delete personal Bayesian data" link I get a RC 'Server Error!' message. I have tried using RC with logging set to 8, but this does not provide any information on this problem. I have checked the SQL statements and MySQL user permissions.