Try to check if the contacts in the camera, where the memory card goes in, are still clean and shiny. Only one with a little oxide on it, can spoil the fun. Only try to clean with a dry cloth and or cotton swabs. If you use oil or contact spray, all contacts will corrode much faster.
If you have the skill to dismantle the camera, you even can go farther, and check the whole path from the memory card contacts to the maim board of the camera.
