Hi everyone. I ordered a Canon EF300mm f/4L IS USM from the store. It arrived last night and the annoying UPS guy never rang the bell so the box spent the night outside in 20 degree cold. I opened it this morning and it had some fogging on the glass but it went away after a short time. I put the lens on my 30D and shot some pictures. I became aware of a noise, a quiet whirring noise that begins when I depress the shutter for the auto focus and continues even after the shot has been taken and the shutter is released. i called canon and they said that it seems like a problem. Now I must return the lens. But it took perfect pictures and I hate having to return it, especially this time of the year. Does anyone have this lens or a similar one and do they know what I am talking about? Thanks!