Given your extensive experience it sure looks like a camera problem. However, to be sure you need to try another battery. Charge and change to the newly charged battery. If you have not tried another battery I say you have a chance of it being a power problem (not enough current for the SR system). Another way you can test - use liveview with SR on (and the new battery in).
BTW did it start at the wedding above? Its obvious in the pic some folks are wet and it was raining. You had a non-WR lens on the K20D but, you could have been under something or using another method to keep water away from the lens. Not blaming you
Hope things work out