Error01 is specifically a lens-to-body communication problem. So it makes sense that the error does not occur when no lens is mounted. So try mounting a different lens, after inspecting the contacts to ensure that there is nothing out of place that might damage the lens. If the error still occurs, it's likely the body-side of the contact system. If the error does not occur, it's likely the first lens (the one that generates the error).
As for the rear LCD, not a clue, but do investigate the battery situation. |
