Because I wanted to use the RB4 pin on a 16F628 I switched of the ‘Low voltage programming’ , but when I went back to try and reprogramme the PIC again, due to wiring changes, it wouldn’t allow me to. 
The Pic programmer tells me there’s no ‘Device ID’ :!: and the 12Volts goes from the MCLR pin, (it’s there prior to me clicking ‘WRITE’ on the programmer display.) I have tried it on a second PIC and the same happen, :oops: call me daft but I did to check it wasn’t a problem with the PIC.
Perhaps this will not help you (because it is not about LVP), but anyway, one never knows : [url]K8048: Reprogramming not possible, possible solution]