can't get memberof filter working

[Gerardo Herzig <gherzig@fmed.uba.ar>]

Hi all. Im having hard time triyng to figure out what is wrong with this
ldap query:

Im triyng to filter a specific user inside a specific group. Like this
/usr/bin/ldapsearch -x -D ".." -w.. 
-b "o=Work" 
"(&(uniquemember=uid=gherzig,ou=People,o=Work)
(memberof=cn=MailUsers,ou=Groups,o=Work))"

It gets no results, but if i remove the memberof part, it works good.
"(&(uniquemember=uid=gherzig,ou=People,o=Work))" as a filter gives me
all the entries that users is in.

What is wrong?
BTW specifiyng a different basesearch is not an option, i need that base
as it is.

Thanks!!
Gerardo