USM & DOGS?

Is it possible that the USM focusing of lenses is bothersome to dogs?

My dog, Bizzie, will sit still as I raise my camera. As soon as I touch the shutter button to focus, though, she splits.

It's not as much a problem if I'm shooting from far away, but if I have, say, the 24-70mm on the camera, she wants no part of it.

Just wondering if the ultrasonic focusing bugs her...

Its the noise from USM that makes her run away.
When dogs face something new, they have only few options, submit to it, avoid it, run away or fight it.
In this case you dont have enough authority and as she does not like the noise so she just wants to go away. Its very easy to get the dog to submit and stay still when you are focusing the lense

Two suggestions: manual focus and/or teach her to tolerate the noise by inviting her to you and feeding her treats while you hit the focus button. The idea is to associate happiness (food and petting) with the noise. Unless the noise is painful to her, she should desensitize quickly. If it is painful, you don't need to subject her to it.