Completely stuck - cannot get pgcrypto to work.

Hi all.
I have spent all afternoon trying to fix this problem and I am
getting nowhere.

I did a fresh install of Redhat 7.3, then installed Postgres 7.3.2.
The problem I have is no matter what I try, I get "ERROR: Load of file
/usr/local/pgsql/lib/pgcrypto.so failed:
/usr/local/pgsql/lib/pgcrypto.so: undefined symbol: px_get_random_bytes"

Can anyone help me resolve this problem ?

The exact commands I used to install and configure postgres are :

./configure
make
make install
adduser postgres
mkdir /usr/local/pgsql/data
chown postgres /usr/local/pgsql/data
su - postgres
/usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data
/usr/local/pgsql/bin/postmaster -D /usr/local/pgsql/data >logfile 2>&1 &

and :
cd ./contrib/pgcrypto/
changed makefile to use "dev".
make
make install
make installcheck
all tests fails.

If however, I dont change the makefile, i.e. I leave it using "silly",
everything works!!!!

What am I doing wrong ?

Richard