I would turn off all the breakers except the MAIN. Then see if the lights are out. I supect the ungrounded conductor from one breaker is tied to the ungrounded conductor of a second breaker. If this is the case, then you would have to turn off two branch circuit breakers.
If the lights went out when you turned off all the branch circuit breakers, then turn the breakers back on one at a time, then back off, to see which breakers are supplying the circuit. Only the MAIN & one branch circuit breaker may be on at the same time.
My other thought is that one of the breakers is stuck in the "ON" position. By disconnect every breaker did you mean that you removed the wire from the breaker or just moved the paddle to the "OFF" position ?