Thread:Project:Support desk/Can't login. No error messages./reply (7)

Maybe something is really wrong with your web server and somehow POST requests are being broken. (Most session related issues should raise some sort of error on special:userlogin)

Do you have short urls enabled in any sort of way that's weird or different from the standard way of doing it? If you enabled editing for anonoymous users, does anon editing go through?