The Ultimate DTT-880HD Territorial freeview decoder of mine stops working recently.

When connecting the TV cable, decoder and TV together, and power on both decoder and TV, the TV screen displays the installation screen (see the embedded screenshot) and is frozen there, no matter how to press the TV remote control.

The decoder unit is frozen also (no matter how to press the buttons on the decoder unit or on its remote control), and its LCD panel just displays either AECt or RECt (the a and r look the same). When turn it off at the wall power socket, it displays the following series of things:
----
boot
CHEC
boot
AECt (or RECt)

The TV and UHF freeview cable have no issues, just the decoder has problem.

It is much appreciated if anyone can help with the above.