PL/pgsql

I am new to Postgresql and am having problems getting functions working.

I have been following an example in the book "PostgreSQL" by Douglas &
Douglas Published by Developers Library.
I put the code in as a function (see end of email)

When I execute it from psql I get the following:
dev=# select my_factorial(1);
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.

Can any one help me find the problem. point me in the right direction?

Thanks
Gene Tuttle

-- Function: public.my_factorial(int4)

-- DROP FUNCTION public.my_factorial(int4);

CREATE OR REPLACE FUNCTION public.my_factorial(int4)
RETURNS int4 AS
'
DECLARE
arg INTEGER;
BEGIN

arg := $1;

IF arg IS NULL or arg < 0 THEN
RAISE NOTICE \'Invalid Number\';
RETURN NULL;
ELSE
IF arg = 1 THEN
RETURN 1;
ELSE
DECLARE
next_value INTEGER;
BEGIN

next_value := my_factorial(arg - 1) * arg;
RETURN next_value;
END;
END IF;
END IF;
END;
'
LANGUAGE 'plpgsql' VOLATILE;