[MySQL] #2014 - Commands out of sync; you can't run this command now

[Antocom]

Ciao ragazzi,
eseguendo questa query:

SELECT tbl.a, tbl2.b 
FROM tbl 
JOIN tbl2 
ON tbl.y = tbl2.y 
WHERE tbl2.b 
IN 
(
SELECT tbl2.b 
FROM tbl2 
WHERE DATE(tbl2.data) = DATE(NOW())
)

mi viene fuori questo errore:

#2014 - Commands out of sync; you can't run this command now


Altre info:

protocol_version	10
version	5.1.71-community-log
version_comment	MySQL Community Server (GPL)
version_compile_machine	i686
version_compile_os	pc-linux-gnu

Grazie in anticipo.
Antonio.