Was the site working before you added the new page type?

You need to login before you run dev/build. You may be getting an error because the system is finding files not registered in the manifest. You need to login from the URL or remove the new pagetype login then re-upload it

http://doc.silverstripe.org/doku.php?id=security#forcing_a_log-in_without_actually_filling_out_the_log-in_form

then re-run the dev build, if you're still getting errors you may have a typo somewhere in your code

I have similar problem while executing tutorial 1 & tutorial 2.

I solve it by executing : http://localhost/SilverStripe/dev/build/

http://localhost/silverstripe/dev/build?flush=1 (with flush) doesn't give new page type on the behaviour.

someone should update the documentation.

vardant - as I've been told it's a wiki so you can change it (or goto open.silverstripe.org and raise a doc bug)