This just started today. I can't walk. Moving the stick does nothing. If I sneak my view does not change. I can switch to third person view and see that my pose does not change if I sneak. I can jump, turn, and even mount a horse if one is within reach. Once mounted I can ride. I can fast travel and open doors if they are within reach. But I cannot walk or run. Encumbrance is not an issue.

I have tried loading older saves, quitting and relaunching, and shutting down the console. None of these work. The game is basically dead to me with this problem. Anyone have a solution?

Using GOTYE on a 2nd gen (old chassis, no card reader) PS3.

To be honest, it sounds like the left joystick on your controller is dead. Have you tried a different controller?

EDIT: Though I suppose that doesn't make much sense if you can control a horse...
EDIT 2: Have you gone through the Knights of the Nine quests yet? There's an animation bug that could cause symptoms similar to what you're talking about. The game might think you're sitting when you're really not. To fix it, you should try finding a place you can sit down (using your horse!). There's several inns and wilderness camps that have outdoor sitting areas.