Try a black-and-white cat: http://pug.komkon.org/04jun/bbchair.html
This guy gets spooked having a lens pointed at him, and jumps and runs when he hears autofocus.
Someone suggested angled flash, which is probably worth trying. Your cats may take off after the first flash, though.
Black cats are just hard. A scene that is overall low in contrast is a must. There is always PS's shadow adjustment tool, or curves.
Joe
