I have been having log in problems for the last few weeks.
Tried changing password process (and plagued the "contact us" button as even the newly delivered password failed to work! and not that I got any response from them either...!). I was going off my head!
But then I tried loging in using IE (Firefox is my usual browser) and got straigt in! SO I thought it must be one of the add-on in firefox. Naa.. never that simple!
Then I came across this topic and I tried the two new 2013 themes. No difference. IE logged in using the XDA 2010 theme so tried that and the 2010 themes and they both worked in both firefox and waterfox.
My conclussion is that there is an additional character being presented in the password field because of an error in those themes (both the 2013 themes).
Just so people know, if you click the "remember me" box when logging in, this will pop a cookie on the browser and will allow your session to carry over (so long as you do not click log off) from browser restarts etc. and should keep you logged in..
Hope this helps someone...
Des. . .