dont know if you`ve had it fixed yet but it sounds like a problem I had last year. the viewfinder blanks out when you turn it to a vertical position, It was caused by a worn cable that runs from the viewfinder into the camera body and gets stretched by the movement of the viewfinder, the spare part cost £90 and took about 2 hours for my local repair shop to fit. hope this helps(posted 8381 days ago)