I put in a GM ticket about this but the response was less then helpful and suggested a macro (which is annoying as hell to fix something like this) so I thought I'd try my luck here.
When I am in flight form but on the ground, I am able to directly go into prowl by just click the prowl button (activates cat form and starts prowling).
However when I am in the air (even only 1cm (or inch)) off the ground and i click prowl I get a error saying I can't do that while in shape-shift form???
Any ideas I'm pretty sure it is a setting or something i can set in game, without having to create a macro.