Maybe i dont understand what you are trying to do. From my understanding you are trying to allow the user to select a row but then push the grid into edit mode? Why dont you just have an edit button? Then you can create the 'editing' method and I believe that will keep your radiobuttonlist intact.

meaning:
on the gridview allow the row to be edited by setting AutoGenerateEditButton to true.

Then in code create the Gridview->RowEditing method. From here you access the radiobuttonlist.

If that doesnt work I think you may have to re work your logic. Might have to make it so you cannot change the radiobuttonlist's selected item untill you are in edit mode.