http://www.pentax.jp/english/news/announce/20110126.html
Quoted:-
"To PENTAX K-5 Digital SLR Camera Users
We would like to express our heartfelt appreciation for your patronage of PENTAX products.
We deeply regret that the first shipment of our PENTAX K-5 digital SLR camera included some products with a stained image sensor — a problem which we believe was caused during manufacturing — causing them to occasionally produce images with spots which look something like water drops, and which users cannot remove with ordinary cleaning methods.
All users of these defective products will receive free repair at our service center.
We sincerely apologize for any trouble and inconvenience this problem may have caused. We also promise to do all we can to achieve the highest level of quality control in the future, and eliminate any worries our customers might have about our products. We sincerely appreciate your kind understanding and cooperation regarding this issue.
Detail of problem:
Spots looking something like water drops may appear on recorded images under certain conditions.
 |  | |
| Entire image | Enlarged image of spots |
*The following information is for customer who lives in Japan. If you are an international customer, please contact nearest service center."
But would this be the end of the story? I am afraid NOT.. Just see a few of all those recent reports by various different K-5 users about the re-occurrence of the same issue after repair/replacement/cleaning of their original K-5 units, as below! :-o It seems that the *root* cause of the issue has not yet been completely located and totally eliminated. >:-(
K-5 Sensor "Stains" Developing Over Time!?
Report of Re-appeared UFOs with Repaired/Replaced K-5 Unit! :-o
LiveView of the K-5 Creates UFOs / Pearls on Sensor?
K-5 Serial Numbers and Issues Summary