Downloaded images become 0x0 resolution

[RazzmatazzTheGreat]

First post on this forum, and if my question is answered somewhere then I apologize for cluttering up the board. I've only had my HTC One for a couple of days, and today was the first time I tried downloading an image someone sent me. At first it worked, and it went to the downloaded folder in the gallery. But later on in the day, if I try to enlarge the thumbnail to view it, it apparently just goes black. By checking the details I can see the resolution is 0x0, explaining why I can't see it, but why is it doing that? I sent myself some images via e-mail just to see if the same thing would happen, and it did. At first I could view them fine, but after around half an hour or so the same problem happened. Any ideas? Is this a known issue, or do I have some kind of setting tweaked to make this stupid outcome happen?