I deleted all the iCloud files, reinstalled the app and now I'm able to play. But, needless to say I've lost all my savegames and my gold purchases.
This is Infinity Blade's Achilles heel. It's a great game, but it punishes long term gamers with this sloppy iCloud game save implementation and no way to restore gold purchases. I'm giving up. I'm not giving this game any more of my time or money. $53 is enough and I should be able to reasonably expect my purchases to be restored after a reinstall. This is not an unreasonable request. 😡 I tried getting support from their website and all you get is a runaround link between FAQ pages. Most unfortunate.