Cannot access "Direct Navigator". "Guide plus" or "Function Menu" ?

Have had a Panasonic DMR-EX88EB Recorder for three years now with no problems. Two days ago however, I discovered I cannot access Direct Navigator, Guide or Funtion Menu via the remote or indeed by any method.. Consequently, I am unable to set any timer recordings or playback any recordings I already have on my HDD. It doesn't appear to be a fault of the remote as it works fine otherwise but I would appreciate any advice anyone could give me.

By the way, I am an 85 year old codger and not very 'with it' regarding modern technology so any answers in plain English please.

Many thanks.