Try logging in again. This time, make sure both the handle and the password field are completely empty of previously saved password(s).
If you type the password manually, make sure you type it correctly. Some fonts display 1 (number one) and l (letter L) in a similar way.
If you copy/paste the password, make sure you don't copy any spaces. To check that, copy it into notepad (or a similar text editor) first and remove any spaces and new lines before and after the password, then copy it into the password field.
If that still fails, try using the Lost Password feature to get a new password.