This is similar to what messed up my apple tv. I had originally jail broken it with seasonpass on a mac (tethered). I attempted to back up my blobs with tiny umbrella but just couldn't get it to connect so I just attempted to use green poison (windows) to make it an untethered jailbreak. It appeared successful but was stuck on the apple logo when booting.Charred Greyface said:It's usually recommended that you restore to the new firmware, not upgrade, when going from jailbreak to stock. That aside, I can't think of anything else. Don't forget to backup first.
Luckily I'd backed up my XBMC prefs before hand but it's still annoying being without XBMC.