MAMP

I’ve setup MAMP using the tutorial on the codex here: http://codex.wordpress.org/Installing_WordPress_Locally_on_Your_Mac_With_MAMP
and all seems to be working well – except it doesn’t

I can get to setup screen at step 4 where i put in
database name: wordpress
database host/server: localhost
database user: root
database password: root

Everything checks out fine and it tells me it is ready to install, but as soon as i click the install button i get an error saying:
“The website encountered an error while retrieving http://localhost:8888/wp-admin/install.php. It may be down for maintenance or configured incorrectly.”

What can cause this?