Buzz from 100-400 L ?

[SnJPhoto]

I was out shooting a race today and had an instance that sort of freaked me out. I was using my 100-400 on a 1Ds and had an instant where it seems the IS started to buzz and gyrate. I just turned the IS off and back on and it was fine. Any ideas what may cause this?

Scott

FYI - here are some of the pics, resized for the web, but no much of anything else.

http://www.pbase.com/snj/vineyard_run_2004

[RichardtheSane]

Which IS mode were you shooting in?

[Jim_T]

Last fall, my 100-400L did something similar on my 10D.. It chattered when I half-pressed the shutter and the image bounced around a bit. The camera shut down with an Err 01 when I pressed the shutter all the way. I turned the camera off and on to reset it, then it did the same thing when I tried to shoot again.

Err 01 means check your lens contacts.. So I took off the lens and gently wiped the lens and camera contacts with a dry lint free cloth that I had handy in my kit. It never happened again :)

Could be you had some grit on the contact that feeds power to the IS..