Update problem

Hi....
Iam facing a strange issue....
One of the functions in my program is running an update statement. The
statement is running cross-schema. What i mean is that the program
resides in one schema where as it updates a table from another schema.
How ever these scehmas are on the same database.
The program runs correctly and also prints out the update statement.
But it never actually updates the table.....neither does it fail.
However when i run one of the update statements individually in the
query tool...the update happens.
Iam assuming that this is not a problem with the permissions either
since the permission for the table to be updated is set to public.
iam pasting the update statement for reference:

EXECUTE 'UPDATE '||thepartition||' SET
volume='||updated_volume||',occupancy='||updated_occ||',speed='||updated_speed||'
WHERE lane_id='||lane||' and measurement_start =
'''||measurement_start||'''';

Thanks
Sam