Google is connecting everything (google+, google search, google docs, gmail, etc.) starting 1 March and implementing some pretty major software changes (at least that is what they say, don't quote me on that
). They have been warning about this for some time now and I just received a mail concerning it about 5 minutes ago.
I would wait for the conversion to be completely carried out and then retry the app and/or look for an update.
Just my $0.02...