Parental control setting is off yet some recordings still not playing.

[notanerd4]

I have a Sony Bravia tv ( 7 years old) and have been making recordings ( onto USB stick) without any problem until recently, the parental lock setting has always been turned off. A few recent recordings (recorded in the early hours)  are not playing back ..i just get this message appearing on the screen… Playback not available. Recording or playback failed due to the parental rating setting on your TV or CAM ( this tv doesn’t have a camera as far as i know).

Has anyone else had this problem and can anyone shed any light on why it’s happening on some recordings and if possible how i can fix it.  
Any info or tips would be much appreciated. Cheers.