Google Authenticator stopped working after I upgraded iphone to iOS5. It crushed right after invocations. My co-worker told me about this, so I was at least mentally prepared.

Actually, it is pretty troublesome as you’ll lose access to Google accounts. Before you’re upgrading to iOS5, here’s what you should do:

• turn-off 2-factor authenticator
• upgrade your iPhone to iOS5
• uninstall Authenticator
• install Authenticator from App Store.
• configure Authenticator

It sounds pretty dumb, but worked.