Autofocus with K30

I've recently experienced a strange problem with my DA 21mm AL lens when used on my K30 body. It suddenly began autofocusing within the one to 2 foot range, after that nothing happens. Can not autofocus on infinity. It happened suddenly. Works fine on my K20D body. All other lenses (Pentax zooms) work fine on my wonderful K30.
Any ideas?

Thank you.

Give the electrical contacts around the lens mount a clean with a cloth, and/or try mounting the lens on and off a few times. Also, check the contacts to ensure they're all standing slightly 'proud' but compress when you press them with a finger nail.