Pentax Formally Apologizes for K-5 Stains
Statement on Pentax's Japan web site
By PF Staff in Pentax Announcements on Jan 28, 2011
Pentax Japan has recently formally apologized for their lack of QA of a sizeable Pentax K-5 shipment, which caused hundreds of bodies to exhibit a "string of pearls" stain pattern on their sensor. Any affected body can be sent to Pentax for repair (sensor cleaning).
All new K-5 bodies should no longer have the issue; before claiming that your body does, please make sure that what you see on the sensor is not simply dust. Before buying a used K-5, please check its serial numbers against those listed in our serial database as defective.
Not all early K-5's were affected by this, but according to the serial database and general forum activity, it's clear that the number of defective bodies is very significant.