f.lux disables itself when it shouldn't
Using Windows 8.1, f.lux 4.104. Frequently when switching the active window, f.lux will disable itself, and then re-enable itself. Sometimes it even pops up a message saying f.lux is disabled for Firefox or for Notepad, even though I don't have those options checked. I can trigger it fairly reliably by dragging jpg files from Windows Explorer into Chrome tabs, it might do it 10% of the time.