With the G-501 error, normally a hard reset and setting up the Slingbox again should fix that. If you're only holding the button down for the 10 seconds suggested, I recommend trying closer to 30-45 seconds instead, just to make sure it's really erasing all of the older data. Also, you can reach out to support for assistance over the phone as well. When you are logged in to your account on Slingbox.Com, you can go to this page:
Once you do, a phone number should populate. Hopefully, holding down the reset a bit longer will fix the issue, but if not, the support hours are 10am-10pm Eastern Time.
I hope this helps!!