When It is asking you to enter the Admin password for the Slingbox, it is actually asking for the password for the Slingbox itself, not the account password. If you cannot recall what this password is you will want to hard reset the Slingbox and set it back up at setup.slingbox.com. For instruction on how to reset the Slingbox check out this link below:
Hope this helps!!
Sling Media Forum Moderation Team