Multiple Pentax k-5 owners have reported stains on their sensors. Pentax Imaging USA have acknowledged the issue and an investigation is currently ongoing:
"I can confirm that Pentax Japan is fully aware of this situation and is diligently investigating the cause of these stains. I’d like to remind our US customers that their K-5 is covered under the 1-year warranty and that we’ll of course honor that. However, until we find out which batch(es) are affected by the stains, we recommend that photographers keep their cameras and refrain from exchanging them for another unit if purchased from an online retailer. Once we fully understand the origin of the stains and how to deal with them we will encourage affected K-5 owners to send in their cameras for warranty repair."
