I think it could well be the card reader as I mentioned before. It might be that it is not liking a larger card but I also find with my nuilt in reader that it is fine with jpgs but won't work with raw files. Given that i use entirely raw files these days, it is somewhat useless so I have an external one that cost under a tenner and works a treat.
Glad you are all sorted now Stepheno.... now show us the colour of your wares
Cheers,
Rob