I had the same problem, Quell not loading on my ipad..
Try opening it from "Game Center" that worked for me & kept all of my info from my iphone play. Make sure you have enabled icloud for it, that way the info will be there from phone to pad.
Actually its the only way I can get into Quell on my ipad because there is no icon for it & wouldnt open from app store.

I hope this works for you !!

Hi Lewis ,
After powering off I still could not open it thru apps... "installed" button was grayed out. But..... I tried going thru the Game Center & SUCESS !!!! It even came up at the level I was on from my iPhone !!!
I'm so happy!!!! Thanks for a terrific game!!!