Automatic Door Lock/Unlock

I have an 2000 Outback that has a problem that I'm wondering if it is a typical problem. On a cold day like we're starting to experience, the automatic door lock/unlock on the key chain will not unlock or lock the car--from the outside. Once I open the car with the key (setting off the alarm) if I hold the key chain inside of the car I can turn off the alarm with it. I'm almost positive it isn't the battery since this never happens when it is warm. I tried the backup keychain and it behaves exactly the same way.

Any suggestions?

Thanks.