As I keep having the same problem for quite a while now - is it possible that it might be connected with the "signup via facebook" feature?
I noticed that the problem seems to be very massive when another tab with facebook is open in firefox, or has been opened during the session. For the record - Windows 7, FF 20.0.1 (and 19.0.2, 20.0.0 before).
I have NOT connected my BB login to my FB account.
Zwei Dinge sind unendlich, die Dummheit und das All...