Have any of you Canon shooters run in to grinding noise when shooting video wth a Canon Zoom 25-105mm lens? Until recently I only experienced normal IS noise while shooting video and slight AF noise when shooting stills. All of the sudden (this lens is about 2yrs old) I noticed loud grinding noise when I sync with extrnal audio in post. It doesnt' seem to affect the image quality, but I can actually hear the grinding and feel it in my hands while shooting.I figured I'd check in with the experts here before I ship this lens off to Canon for a diagnosis. I appreciate any comments. Thanks!