extensions.torbutton.regen_google_cookies;false
extensions.torbutton.reset_google_cookies;false
extensions.torbutton.xfer_google_cookies;true
Try changing this last setting
(extensions.torbutton.xfer_google_cookies) to false. It is designed to
try to move your google cookies from one domain to another to avoid
requiring you to solve captchas for every google country domain.
It could be breaking something in the signon process, especially if
you get redirected to/from a country domain during login (by using a
german exit, for example).