2003 MDX Battery drain - radio stays on?

I recently developed a battery draining problem - the radio stayed on when I shut off the car - even when I manually turned off the radio and removed the key, the battery drained in a couple hours. The radio used to work normally - IE turned off when the car was turned off. I had the car at a transmission shop (imagine that) and after an $850 torque converter bill, the mechanic thought the electrical problem is related to the security system and the online monitoring? Anybody ever hear of that? I didnt think that an '03 would have "homelink or onstar"? Any way to disconnect it or reset it?

I am at wits and checkbook end with the car. It doesnt have nav, but does have the DVD. Could there be a relay that is sticking? The radio will stay on until the battery dies, so it is not a time issue.