problem with CREATE FUNCTION

I'm trying to create a function for dynamically calling plsql functions,
and I can't debug it due to a problem with postgres.

My c function compiles fine.

I execute:

CREATE FUNCTION myfunc (text)
RETURNS text
AS '/myfuncs/myfunc.so'
LANGUAGE 'C';

and then a simple run of the function:

SELECT myfunc('some text');

It works.

Now, change something in the function, recompile, and postgres continues
to use the old code. I've tried dropping the function, and recreating it.
I've tried renaming the shared object file. It doesn't work. Am I
missing something?

Although, all of this wouldn't be necessary if someone would tell me how
to dynamically call functions in postgres (see my previous post regarding
"dynamic sql..."

Thanks,

R.