My third screen 5600T is showing comm frequencies x'd out although when I touch the box I can change freq, toggle, go to nav and everything operates. Strange that Nav freq will show in window if I leave it on Nav. But switching back to comm freq displays X. I have done some troubleshooting:

Screen set to 177, looks at afs comm screen( tried both)
Afs comm is set to on, and correct with ser no (identical to other screens)
Reloaded current software
Network cable good
All other windows populate data

So what causes that window to X out even though it displays nav data and processes comm data?