Dazed and Confused

I have just upgraded Postgres from version:
PostgreSQL 7.2.3-RH on i686-pc-linux-gnu, compiled by GCC 2.96

to:
PostgreSQL 7.3.4 on i386-redhat-linux-gnu, compiled by GCC
i386-redhat-linux-gcc (GCC) 3.2.2 20030222 (Red Hat Linux 3.2.2-5)

All of my trigger code loaded successfully; however, I am now trying to make a
change in some of the trigger code and cannot. When I try to reload the code
as in, \i cust/cust_preupd_func.plsql, I get an error. The error is:
psql:logs/logs_preupd_func.plsql:132: ERROR: ProcedureCreate: cannot change
return type of existing function.
Use DROP FUNCTION first.
I didn't change the return type at all. In fact, if I try and reload any
trigger code by the method above, I get the same error even though I didn't
change a line of code.

All of my trigger functions return OPAQUE. I notice from some of the examples
in the docs, i.e., Example 19-1. A PL/pgSQL Trigger Procedure Example, that
the return type is TRIGGER.

Am I going to have to change all of my trigger code?

Thanks for any help you can give...
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email: terry(at)esc1(dot)com