No content types showing under 'Add content'
I found this :
http://drupal.org/node/997444
it seems like it's a very strange behaviour. 

Basically I guess Drupal looks at that specific main menu to see what types of content can be created by users, so if even if you move all the options to a different menu none will be available.

I had to re-add the add-content link to the administration menu and re-check all the submenu items, then set it to display:none; and add the 'Add content' link to the user menu again.