BCS - add item form for creator method not working

You have created a BCS model, added a creator method to it but it is throwing an Runtime Error. In the logfile you find "SPException: Unable to find the default new form for list"

A probable reason for that error is the following. You created the model only with a ReadList and ReadItem method. Then you created a list in SharePoint and tested that functionality. Then you added a creator method and used the previous created list to add an item. That does not work because the list was provisioned without the "new form". Just delete the list and create a new one. The "new form" for the list should show up as expected.