The image stabilization on both my 24-104 f4 and 70-200 f2.8 IS is acting very funny. I have owned both lenses for several years so I know what normal IS operation sounds like. In the past two weeks, both lenses have begun emitting grinding noises when the IS engages. In addition, the image in the viewfinder visibly stutters in time to the grinding noise.
The problem is most apparent when I half-press the shutter button, IS engages, and then I zoom. The lens begins making a horrible grinding noise that I have not heard before. Today, I noticed the 24-105 making the grinding noise even when I stay at 24mm and half-press.
Disengaging IS makes the problem disappear completely.
The lenses exhibit the problem on both my 40D and 20D bodies, so I suspect it is an issue with the lenses and not the bodies. FWIW, my 40D is upgraded to the latest firmware (1.08). I have not been to any sandy locations recently, so I can't imagine that it is sand in the lenses.
Anybody else have this problem? I tried googling to no avail so I wanted to try here before contacting Canon Service.