Thanks for using the forums. Are you connecting the Slingbox via wifi or ethernet? How far away from the router is the Slingbox? If you are too far away from the router, the Slingbox may not be able to do the update. You may want to try to hard reset the Slingbox again one time time, holding the button for 45 seconds. If it still cannot finish the update, you will want to hardwire the Slingbox to the router and it should be able to finish the update.
Hope this helps,
The Sling Moderation Team