This is an ongoing problem when stray code gets in the system. There was a thread on it a couple of months ago. Unfortunately, you need to reset Guideplus.
On front of machine, hold down STOP button, then press and Hold STANDBY/ON. Release STOP. Will reset Guideplus, but you will not lose anything you have saved on the HDD.
It is a bit of a pain to do this, but it will not right itself. This was advised by a Pioneer Engineer who said he reset his machine everycouple of months!
Good luck.