I have a GridField in my getCMSFields function for a subclassed page that's similar to the example in "Customizing Detail Forms" on this page of the documentation:

http://doc.silverstripe.com/framework/en/reference/grid-field

The code worked fine in SS 3.0.5, but with SS 3.1 I get the following error when I try to access a page of this type in the CMS

Call to a member function stat() on a non-object in httpdocs/framework/model/DataObject.php on line 3192

Any clues?

In case anyone else runs into this problem, as best I can tell the API for GridField changed with v 3.1 See -

http://doc.silverstripe.org/framework/en/reference/grid-field

The doc must have changed since I first posted my question because this is the same url referenced below.

I replaced my config setup for GridField in getCMSFields() with this line-

$config = GridFieldConfig_RecordEditor::create();

And defined my columns with the summary_fields property of the class used for the DataList and no longer have errors in the CMS.