Galaxy Ace 2 won't display images due to lack of memory?

I have a Samsung Galaxcy Ace 2, and it doesn't display images due to lack of memory, as it says. When I open the gallery app, it says "There is not enough space (__ mb) in your device memory. Delete some files." Whenever I do so, it's still not enough. I have this problem a lot, and I delete most of my unnecessary files, and it remains unchanged, usually, and rarely actually displays my remaining images. My device memory is 1 GB, and I have an 8 GB memory card, and most, if not all my things are on the memory card. Can anyone help me with this? I have no clue anymore, and alternative solutions just don't seem effective to me at all.