After a little research, we actually found out Sigma had a location right by us on Long Island. My dad went there today, told the tech what was happening. He took the lens and within 10 minutes he came back with it all fixed. Said he had to adjust the Af/Mf Switch. Maybe there was a loose wire or something, but it's all fixed now. Thanks for the responses guys. He also said we should shut the OS off everytime we turn off the camera for some strange reason. Not sure why, but might as well forward what he told us onto you.