1. Are you sure the card is good. Does it work ok in PC's or slots other than the one it was loaded on?
2. Suggest maybe moving the files off the card and reformatting the card. You might try FAT32 as the format. 3 Ways to Format an SD Card - wikiHow
... then reload the jpegs and try again.
3. Does the unit recognize other files like mp3's on the same card or does it not load at all?
4. Personally...I'd try a different card (not over 8GB) and see if the situation duplicates itself. If it does...it's a unit problem. Try the reset as noted...then send it for service if you can.
There is supposedly a new unit being introduced by someone within the next month or so that will replace the Genesis & others. If you find the GT3 needs replacement...you might wanna wait a little bit cause whatever they announce
HAS to be better than the current stuff!