I had this k550i for few months now... My sister had the same phone and she had this camera problem, and she brought it to the phone shop and they changed a new camera for her saying that she cracked the camera.. And now i also had the same problem... But if i cracked my camera lens, why is the lines looks the same as my sisters? It's impossible that our crack is identical or so... Anyway, i was taking pictures when it occurs... The lines came out suddenly... Anway here is the link to the pictures of the faulty camera...

http://seanpohtemporary.blogspot.com/