the blackscreen happen often when portal freez up while loading options 1. reboot the box whit stb open ( unplug power cord wait 15 sec plug back)
2. stb reset clear cache for the app and clear data...
when that happen restart the box and start al over whit the password and user again it work for me 100%
make sure you dont have another device wuit the same mac and service connected. or it will keep cuming up password and user .
That doesn't help I have freezing channels since 9 speed test 75MB reset mac doesn't help.
Spanish channels freezing the most the rest freeze enough to make you turn it off and catch pokemon.