Gnus blocked by Gmail?

[Thorsten Jolitz <tjolitz@gmail.com>]

Hi list, 

I asked this before on 'gnus.user' but got no replies, so I try it here
too. 

Since a few days I cannot access my gmail accounts anymore via
gnus. Everything else works (accessing gmail from web-ui, reading
newsgroups with gnus, using msmtp from the command-line), but for my
'nnimap+xyz:INBOX' accounts I only get 'access denied' from the server.

It worked for a long time, and suddenly stopped without any apparent
reason (I did not update gnus or so). 

Now I wonder if maybe Google blocked gnus due to frequent access (its
just too easy to press 'g' in the Group buffer, and I have several gmail
account that are fetched each time I do so)? Did this happen to somebody
else too? How can I find out what is the real underlying problem here (I
cannot find any informative error messages or logs, even when running
gnus 'verbose' the enormous output isn't really enlightning)?

Are there any files I could delete to force a reset or so? Its really
uncomfortable to manage emails without gnus, so any hints would be
welcome. 

PS

#+BEGIN_SRC emacs-lisp
(emacs-version)
#+END_SRC

#+results:
: GNU Emacs 24.3.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.12.2)
:  of 2014-06-11 on var-lib-archbuild-staging-x86_64-jgc


#+BEGIN_SRC emacs-lisp
(gnus-version)
#+END_SRC

#+results:
: Gnus v5.13


-- 
cheers,
Thorsten