My girlfriend has a 1997 Honda Civic EX. For some reason, if she tries to manually unlock the door with the key the alarm goes off and the car won't start. She has to unlock it and lock it with the keyless entry. Any ideas why? We're going on a trip next week and we don't want to risk being stuck without a car if the keyless entry breaks (a backup remote is $90 from the dealer- I'd rather just use the key).

Thanks a lot.