Call me stupid (no, really), but I can't find clear rules on what dispel magic (or similar) does to a magic device trap. Symbol spells of course function as spells and everything seems very clear cut.
Do magic device traps simply function like magic items? A successful dispel magic would make it cease to be magical for 1d4 rounds? I'm guessing it wouldn't dispel it permanently.
Our group treats them like magic items, yes. Dispel suppresses the trap temporarily and a disjunction type spell would remove the permanently.