Sometimes your password will contain letters that are hard to distinguish, like a capital letter O or the digit 0.
Try to copy and paste your login information to make sure it's not working. This works about 99% of the time. If it doesn't work, use the messager in the lower right hand corner to let me know.
To copy: Highlight the text you want to copy, then right-click and click "Copy."
NOTE: It's VERY important that you don't copy an extra space before or after the text you want to copy.
To Paste the text you just copied: Right click in the text box in the login page and click "Paste."