Originally Posted by t-mug
The same for me. Except I enable the "show validation bar" of the web developer plugin (in german it is: Extras => "Seitenvalidierungsleiste anzeigen"). Instantly the admin login is not possible any more and I get "login.php?err=" in the address bar. Please try it out.
I was just now reading this thread to find out why my login was not accepted, and this was the reason: if one enables "site validation" in webdeveloper, the login is refused.
This info may not fix the original problem, but can clarify some others.
FYI, I'm using WT in Brazilian Portuguese.