Autofocus no longer working

Has anybody had any issues with a 50mm Pentax SMC FA 1.7 autofocus lens no longer functioning as an autofocus? It worked when I first bought it (ebay) but now it isn't recognised as being an autofocus lens or having an 'A' setting on the aperture ring.
I've tried it on my K10 and ist DS and it's the same on both...

I've seen it mentioned here to take it off the A setting and wind the aperture ring back and forth a few times. Then make sure all the contacts on the lens and the camera body are clean (i.e. clean them carefully). Put it back in A, then try it again.