I use a Call DB proc in my transformation which generates the following error:

2007/11/06 13:49:43 - Call DB Procedure.0 - ERROR (version 2.5.0, build 25002 from 2007/04/25 10:37:12) : Unexpected error in ' : java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
2007/11/06 13:49:43 - Call DB Procedure.0 - ERROR (version 2.5.0, build 25002 from 2007/04/25 10:37:12) : java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
2007/11/06 13:49:43 - Call DB Procedure.0 - ERROR (version 2.5.0, build 25002 from 2007/04/25 10:37:12) : at java.util.ArrayList.RangeCheck(Unknown Source)
2007/11/06 13:49:43 - Call DB Procedure.0 - ERROR (version 2.5.0, build 25002 from 2007/04/25 10:37:12) : at java.util.ArrayList.get(Unknown Source)
2007/11/06 13:49:43 - Call DB Procedure.0 - ERROR (version 2.5.0, build 25002 from 2007/04/25 10:37:12) : at be.ibridge.kettle.trans.step.dbproc.DBProc.runProc(DBProc.java:96)
2007/11/06 13:49:43 - Call DB Procedure.0 - ERROR (version 2.5.0, build 25002 from 2007/04/25 10:37:12) : at be.ibridge.kettle.trans.step.dbproc.DBProc.processRow(DBProc.java:122)
2007/11/06 13:49:43 - Call DB Procedure.0 - ERROR (version 2.5.0, build 25002 from 2007/04/25 10:37:12) : at be.ibridge.kettle.trans.step.dbproc.DBProc.run(DBProc.java:205)

everything looks fine (connection, db etc etc)

the function i try to call:
CREATE DEFINER=`henk`@`%` FUNCTION `werktijd`(create_date DATETIME, close_date DATETIME) RETURNS int(11)
DETERMINISTIC
BEGIN
DECLARE m1,tmp INT;
select count(*) into tmp from d_date where werkdag = 'N' and datum > create_date and datum < close_date;
set m1 = tmp;
RETURN m1;
END;

works in the db. input is never null.....

what goes wrong??