I am having the exact same issue Ryne. I tried every form of restarting my phone and app. If I uninstall the game then reinstall it, I found I could play on a temporary account name but as soon as I tried to log into my game center it started crashing as soon as the app was launched again. They really need to fix this... it's super frustrating. Please update if it starts working for you or you find a fix.
I am having this same problem on my AppleTV version of Risk. What version are you using?