Strange behavior after refreshing stored functions

Hi All,
I have a very annoying problem at one of my customers.

The phenomenon is the following:
I run all function refresh scripts (create or replace function exrpssions)
and trying to use them.
Sometimes it seems nothing has happend to the database and the functions.
They work just the same way as before. The only way to have them work is to
dump out all the database, drop the database, recreate the database and
restore the whole thing - the same dump file. After this it works as fine as
I except.

What can be the problem with it? I do not like to go on site for every
program refresh to dump out and back the whole database. There must be a
better solution.

(system: postgres 7.3.2 on RH7.1)

Thank you for your help.

Best Regards,
-- Csaba