Key won't turn in the ignition after battery replacement. Any ideas how to fix?

What is your question?

The van started 6-7 times after replacing the battery with no issues. I've tried resetting the anti-theft system using the fob and trying to lock and unlock the drivers door with one of the master keys. My wife started the van with the valet key, turned the van off, then was unable to turn the same key in the ignition a 2nd time. I've disconnected the battery, checked the necessary fuses and I've had no luck getting the master or valet key to turn the ignition cylinder. The van is an "03 EX model with only 80,000 miles on it and is driven regularly but not abused. Any help or ideas would be appreciated. Thanks, Toby W.

What makes this problem better or worse?

Started after a battery replacement.

How long has your 2003 Honda Odyssey had this problem?

6 days.