The only requirement for the password for a Slingbox account is that the password is at least 6 characters. This can be any mix of letters, numbers, and special characters. I've linked an article below that goes over the full password change/reset process, just for ease of access:
Please be sure to stay on the verification page that populates after adding your email address and clicking the "Email Me" box. If you leave this page, the verification code becomes obsolete and you will have to begin the process over.
I hope this helps!
Sling Media Technical Support