rare thing on 2003 chevy silverado

I installed a RS 900LCD. (autopage remote starter and security combo) on 2003 Chevy Silverado, I also used  a GM-SL2-i to interface with power door locks since this wasn't a base model truck.  everything came out fine.

One day after the installation, the battery in this truck got discharged. The customer called after he tried to get in the truck using the key. but it did not work. 

I went to his address and jump started the truck. Everything went back to work, but the key (or key hole)  does not longer work when I try to unlock the doors. but the door locks  work with the alarm remote transmitter and the factory remote as well.

I hope i explained my self.

Thank you again to all of you pros out there.!

I think this is something else, because the door cyliders worked fine before. this truck is almost new, it only has like 12k miles on it. The customer does not drive it, unless it's sunny outside, and We live in Seattle!! ha ha (rains a lot here) ....I don't know, probably something to do with the factory alarm, on-star system, ???? 

Sounds as if something is mechanically wrong with the door cylinders. I doubt the alarm on onstar has any effect on the door cylinders, just a coincidence.

ok thank you very much!