It sounds like she just doesn't like being in an arena, and has learned she can shut down in there, and doesn't have to work.
I'd suggest you start from the 'ground-up' on the arena work...instead of trying to ride her immediately, go to the arena and do ground work; longing, bending, flexing, yielding, etc...from the ground; get her to start unsticking her feet from the ground, THEN start focusing on getting back on her and riding her in the arena. Have someone longe her with you on her for a while, then move from there.
I would also work within her 'thresh-hold' time, when you do get up to ride...if you already know she only goes about 10 minutes, then go five, get off, and call it a 'day' for arena work; go out and trail ride after that, if you want to keep riding.
If she refuses to move for you, instead of trying to force her foward, try getting her to yield her hip to you; atleast then you are able to keep her feet moving, rather than her standing there getting fed up with you kicking, clucking, or whipping her, and eventually moving off bucking.
Last edited by mom2pride; 06-07-2009 at 11:38 PM.