DA* 55mm suddenly not auto-focusing on a K5

Petroglyph wrote:

My DA* 55mm f1.4 has been calibrated and working perfectly for some time now.  All of a sudden the lens hunts and won't lock in focus.  I've not had that happen before and have taken a lot of images over time.  It hunts in low light also in relatively good light. Focus only locks in on about 1 in 10 tries.  I changed batteries same result.  I put my Tamron lens on the camera and the Tamron still focuses perfectly on every try under the same conditions - so it isn't the camera.  Anyone have some ideas as the focus motor still seems to be in operation?  I'll take an FA43mm to my next but this is my only weatherproof lens.  Suggestions appreciated.