There was a problem with the zoom mechanism on my EF-S 17-85 IS where it was stuck between 35mm and 50mm. Didn't have any idea what could be causing it. Now, the zoom moves fluidly enough across the whole range, but there's now something stuck inside the lens. and it's rattling away. Does anyone know what it could be and would it be a big job to get it out of there? Please reply as I really want to sell the lens and I want to get at least 300,000 KRW for it!