On my Gentoo box until today I had dovecot-1.0_rc7 and used following entry in /etc/dovecot/dovecot-sql.conf

password_query = call Authorize('%u', '%n', '%d')

Simply put dovecot is calling my mysql stored routine which handles authorization. Until today, when I updated dovecot to  dovecot-1.0_rc8 it worked flawlessly. With this version executing stored proc dies with:

Password query failed: PROCEDURE mailsql.Authorize can't return a result set in the given context

Replacing stored proc call with select .... statement does the thing, but it's stored procedures are ... generally better to do things on DB imvho :-)
Downgrading to dovetot-1.0_rc7 fixes the problem immediately. Of course /etc/dovecot/dovecot.conf remains the same in either case.
Is this a bug or change made on purpose?

--
Chaos greets U