Here is what works for most people:
1. Open Internet Explorer
Clear all cookies and cache.
Try logging in with your username and password.
2. Open Firefox (http://www.getfirefox.com)
Clear all cookies and cache
Restart the browser (Close completely out of it, then restart the program)
Try logging in with your username and password again.
If you reset your password, you will need to wait 5 minutes, then check your SPAM folder for the instructions or the new password