Why are the iPad games Epic Citadel and Gravity HD crashing on startup?

I've got 2 iPad games that crash (vanish from the screen) on startup. The games are Epic Citadel and Gravity HD. Both apps go through the loading sequence then the screen goes black and returns back to the main iPad screen. I have tried reinstalling Epic Citadel with no luck. I don't want to delete and reinstall Gravity HD as I would lose where I am up to. I have raised a support call with the latter game but have not heard anything (2 weeks ago). Any ideas on what to do?

Solution 1:

Try rebooting the iPad to free up some memory. Hold the lock button until the "slide to power off" slider comes on, slide it, then turn the iPad back on.