If you have this feature turned on, and you edit a preset, the unit will do this when you try to change away from the preset without having saved the changes. It's a safety feature that is, IIRC, on by default.
You can turn it off under the Global Settings.
Rebooting the unit clears the edited state of the preset which is why rebooting it "worked" but is technically a sledgehammer to a nail.
You'll want this OFF before you perform with the unit as doing things like using your wah and what not can cause the edited state to be triggered which would then prevent you from then changing presets mid-performance.