The full error message reads “Failed to get value of the “Approval Status” column from the “Moderation Status” field type control”. This error has started occuring on document libraries containg web part pages that were upgraded from SPS 2003. The Hidden property on the Approval Status field has somehow been set to false. The Hidden property should be True.
I found this fix. Download a utility called SharePoint Manager 2007 from this site.
Run the application on a SharePoint server.
Go to View – Object Model and make sure “Full” is selected.
Browse to the library in the treeview.
Open the list of Fields and select the Approval Status field.
Change the Hidden property to True.
If the property is already set to True then change it to false and save it. Then change it back to True and save again.