Can't use certain mods (Num Lock turns itself on and off)

For whatever reason, my Num Lock likes to turn itself on and off at its own will. Sometimes I'll be in a patrol, press something like Num0 (nowhere near the Lock button, so I know that's not the issue), and activate whatever it activates, then press Num1 (again nowhere near the Lock button), and it won't work. I press the Num Lock key, then Num1 again, and it works. I never turn my Lock off, so why does it appear to be turning itself off?!