Quess you have a property that have an CreatePropertyControl() that don't inherit from PropertyDataControl
I had a custom PropertyDataControlAdapter and had to override ShouldCreateDefaultControls() to return true to get them to work
In my case it was a webcontrol that inherited from PropertyPageReferenceControl : PropertyDataControl. So both custom properties, webcontrols and control adapters can be the guilty who gives the error.
Can anyone shed any light on this error that I am now getting after upgrading the site from CMS6 to CMS6 R2?