Camera Problems

my camera on my 9900 worked fine since i got it but now i noticed that every time i click to start it i get a black screen and a mesage comes up saying "could not start the camera. close other applications and try opening the camera again". i closed all the applications i can and that didnt work. i tried to take the battery out and put it in again and that didnt work. i tried to install the latest OS and that didnt work. has anyone had this problem before and if so how would i fix it? i should have a 1 year warretny and i have about 6 months left so i could warranty it but i dont want to send my phone out for couple weeks for them to fix it