I've read about people - the most recent being RingKingLeo - having issues with the log-in screen due to the erratic behaviour of the forums. I experienced this for myself today. After entering my username and password, I was told that I had made "too many login attempts", when I hadn't, and asked to enter a captcha, but the page went back to the login screen before the captcha was displayed. Even if you time it right and click stop before the page refreshes, the captcha is never displayed.
Here's a quick tip to get around the problem if this ever happens to you.
1) Enter your username and password.
2) Hover your mouse over the 'stop' button on your browser and hit the 'enter' key.
3) As soon as you see the red error message page load, hit stop.
4) Save the web-page to your desktop but don't close the window.
5) Find and run the web-page from your desktop (file name 'ucp.php')
6) You'll see that the captcha is displayed and that the page doesn't refresh.
7) Now enter that captcha on the original FC forum login screen that you left open.
Assuming you entered the correct username and password, you should now be logged in.