If Photosmith is frozen on your iPad, and nothing you do, either hitting the home button or the power button, does anything, try double-tapping the home button as if you are fast app switching.
Double-tapping the home button should bring up a list of your most recently opened apps along the bottom of your screen. Photosmith should appear as the left-most app icon.
Tap and hold the Photosmith icon until it starts squirming. Then tap the red X to put it out of its misery. Tap the home button once more. Sanity should return to your iPad.
We may have discovered some kind of bug in iOS that allows apps to hang iOS in ways they're not supposed to. We call this the "stealing home screen" bug, and it's not ever supposed to happen. Ever.