BUG #6122: Installation fails: "database cluster initialisation failed"

The following bug has been logged online:

Bug reference:      6122
Logged by:          Mike Holywell
Email address:      mike@segment8.co.uk
PostgreSQL version: 9.0.4
Operating system:   Mac OSX 10.7 (Lion)
Description:        Installation fails: "database cluster initialisation
failed"
Details:

On a fresh install of Lion (11A511) installing Postgres 9.0.4 fails
    Problem running post-install step
    installation may not
    complete correctly
    The database cluster initialisation failed

This has been reported on other blogs eg

http://seeboriscode.blogspot.com/2011/06/osx-107-lion-postgres-installation.
html

I've had a similar(?) problem with the dscl command not creating the user
under earlier Lion Betas