7.4.1 install problems on OS X 10.3

Hi,
I have been forced to re-buid postgresql 7.4.1 but am encountering a
problem when i do the following:

1. /usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data

the error I get is as follows:

fixing permissions on existing directory /usr/local/pgsql/data... ok
creating directory /usr/local/pgsql/data/base... ok
creating directory /usr/local/pgsql/data/global... ok
creating directory /usr/local/pgsql/data/pg_xlog... ok
creating directory /usr/local/pgsql/data/pg_clog... ok
selecting default max_connections... 10
selecting default shared_buffers... 50
creating configuration files... ok
creating template1 database in /usr/local/pgsql/data/base/1... FATAL:
could not create shared memory segment: Cannot allocate memory
DETAIL: Failed system call was shmget(key=1, size=1081344, 03600).
HINT: This error usually means that PostgreSQL's request for a shared
memory segment exceeded available memory or swap space. To reduce the
request size (currently 1081344 bytes), reduce PostgreSQL's
shared_buffers parameter (currently 50) and/or its max_connections
parameter (currently 10).
The PostgreSQL documentation contains more information about
shared memory configuration.

initdb: failed

Any ideas as to how I can rectify this, taking into consideration that
I am a complete novice in the wonderful world of unix ;-)

regards

Uzo