Password is caps lock sensitive, if you write a small letter where it should be a big one or other way around it will be seen as the wrong password. Also if you have numbers in your password, make sure you use the numbers above the letters instead of the numpad since they don't work either.
In general everyone should keep their usernames and password away from symbols. numbers and spaces all over the place to keep it simple.
If you are still unable to login you should take Windance suggestion by changing your password through your forum profile, and if that fails create a new account since it might be the name and not the password.