Default [Q] Dust in Camera

Hi guys, I have a huge amount of dust in my camera and a small black area which can appears for no reason (it exists on stock rom, custom rom, now on cm9). Black area can disapper and appears in different places and in different shapes (now it is near camera swapping button)
Anyway I want to know is there is a way to get rid of the dust ? Where they enter my phone ? Are there anyone have same problem ?