INSTRUCTIONS TO FIX:
1) Remove any flashlight apps you might have installed.
2) Reboot the phone. (hold power switch, wait for slide to power off, slide, turn it back on once it turns off)
3) Install "Flashlight by Rik" from the App Store. After trying several flashlight apps, this one didn't seem to cause the problem. On top of that, it's free and has absolutely no ads, and is much faster than any other flashlight app I've ever used.
It was like a double-win, fixing my problem and getting rid of my old ad-infested flashlight app.