Menu, USB, USB File list
navigate to current file, OK, S/W update,OK  and wait
Reciever will say writing then write with a counter to 100..
Do not disturb this process
After finish, navigate to yes, then OK
Unit will reboot and will start to work again, 
You may need to wait for new keys to enter the unit.. 5-15 mins usually

Use the remove device safely option to remove your pen drive..

menu, usb, remove device safely, OK, then pull out your pen drive and reattach your hard drive if so equipped