I understand that you are having some issues with the Slingbox password since it does not seem to work.
The first thing to try is to reset the Slingbox. This way, you will be able to create a new password (or use the old one). If you do not know how to, just check this link:
If the issue persists, I recommend you to check the following link in order to know if your Operating System and the web browser combination are supported: