This error message occurs if you are trying to update results in D_Page when D_page is configured as read only. Is this your scenario or else could you please explain me the requirement what you are trying to achieve.
If possible config screen shots so that it will be easier to understand.
The error is not related to data page . However I have found the root cause for it .
Root Cause: In an activity , user was looping on a value list . In a child step of the loop a property set was being done on a temp page without creating the temp page. The error was happening while doing a obj-Save on the temp page.
Fix- I added a step to create the temp page before setting the values on the temp page.
We can also create a temp page with the same context and try to copy(using page-copy) the details to temp page and perform save on latest temp page.
This issue is happening as we are performing series of actions on the same page.
Try this once.It worked for me.