Guys, I'm having a bit of trouble with my 200mm lens. Sometimes (indoors, early in the day) it works great and other times, I push down 1/2 way, the camera seems to focus in - "BEEP" - it's focused and I push down the rest of the way and it produces this - (times are aprox.) At 3:00 PM.... 2:00 PM....with less smog 4:00 PM....... I've tried everything I know....I can turn the AF off and focus on flowers and stuff that way, but I'm shooting some motorcycle action this weekend and I don't have a clue. When I first went out shooting with it a month ago it was, of course, fine. The only thing I can think of is that it's atmospheric interference. We've had some code-don't-breathe days here north of Atlanta, and that shot was taken around 4pm....and the air is thick with haze/smog. Is that the problem?