prepared statement not working

Hi,
i try to get the follwong statement executed as an prepared statement.
It delivers 0 results.
The same statement, executed as a non prepared statement does return the
correct data.
Any ideas?


     select
a.id,a.partnertyp,a.firmakurz,a.partnerstatus,a.adminstatus,a.eklassen,b.ort,b.plz,b.strasse from partner a, adresse b
wherea.isdeleted=0 and a.id=b.partnerid  and a.partnertyp !=6 and a.eklassen like '%20:%' and b.typeid=1 and b.plz in
(selectc.plz from plz c,baseregion d  where c.bundeslandid=d.id and d.id=4 ) order by a.firmakurz; 


Kind Regards

Jürgen Lüters