Camera roll photos won't show up or open after 8.1

[WPCentral Question]

I am using Nokia Lumia 520, and after the 8.1 update, none of the photos from camera roll on the SD card would show up through the photos app, and they cannot be opened through apps like Pocket file manager. Previously, I could preview these photos as icons and open these photos in my Windows PC (Windows 7) and programs like Painter and Photoshop, but now I get a error saying the file format is incorrect. Some of the image files that I had transferred from my PC before the update also have this issue but not all of them. This was an issue in 8.0 when my SD card wasn't properly formatted but hasn't happened until this update. New photos taken after 8.1 are fine.

If anyone has any solutions for how to get these photos working, I would appreciate it.