Have a look at the follow article to reconfigure a Slingbox remotely:
Even though you do not have a new cable box, these steps will still work.
The above article is only if you can connect to your Slingbox. If you go to accounts.sling.com and then click on "Slingbox Directory", if there is no Slingboxes listed, you will have to be at the home location to reconfigure the Slingbox.
The following article will explain how to reset your Slingbox:
After the reset is done, please go back to newwatch.slingbox.com to set you Slingbox back up.
Hope this helps!!!
Sling Media Moderation Team