I can't seem to login anymore, I have downloaded and re-installed the app, but keep getting this message (yes, I even reset my apple ID password): "Could not sign in. The server encountered an error processing registration. Please try again later." When I try to delete the app, I get this: "Messages.app cant be modified or deleted because its required by Mac OS X." I cannot sign in, so I cannot use it, why? Is it still working for everyone else?