In addition to the supplied templates, I always create some extras to give clients flexibility. On this particular one, the client asked for some very specific, and large, templates for upcoming events and photo display. I made these for him, but he now can't use them as, whenever he starts a post using one, it refuses to save. Smaller templates (Left Image, Right Image, etc) work fine for him.
I can use these templates so I know it isn't the template itself, but I can't think, on his end, what could be causing this. It sounds like a max file size or something like that. He cannot even open one of the larger templates, add JUST a title, and save - it crashes. Template IDs are 7, 8, and 10.