I would unplug the unit on G1-3 for a few minutes, plug it in and let it go through boot up and leave it alone for 30 minutes. This should restore the guide. If you go to options 6,0,5 then toggle the right arrow to diagnostics F, you should see numbers in row 1 and 2, mine looks like this today, Thurs and has the guide fully loaded.
d: 8- 0 0 0 0 7 7 0 0
8- 0 0 0 0 7 1 0 0
The 7 over 7 means program title & info is loaded fully for that day.