I had the same success using 7.3.2 with Cygwin:

e=# SELECT functest1('A','B'), functest1(null,'B'), functest2('A','B'),
functest2(null,'B');

functest1 | functest1 | functest2 | functest2
-----------+-----------+-----------+-----------
A | B | A | B
(1 row)

e=# select version();
version
----------------------------------------------------------------------------
----------
PostgreSQL 7.3.2 on i686-pc-cygwin, compiled by GCC gcc (GCC) 3.2 20020927
(prerelease)
(1 row)

George

- snip -


---------------------------(end of broadcast)---------------------------
TIP 5: Have you checked our extensive FAQ?

http://www.postgresql.org/docs/faqs/FAQ.html