Trying to program a PIC18F452 in circuit

[12 Cents]

Hello,

lately I have started to put together a PGA2310 based Preamp as discussed some time ago in this thread: New Digital Pre-Amp . The designer's website is here where board layouts and schematics can be found also.

I have problems programming the 18F452 I use in the main board circuit. I built the PPWIN parallel port programmer as shown here .

For programming I use IC-Prog. Now when I test the two LEDs using IC-Prog everything works, the hardware settings are as described on the PPWIN website, but when I connect the PIC using the ICSP header on the PPWIN board I cant program the PIC, everytime it breaks with "Programming failed at adress 000000h".

Maybe some points:
1) When testing Vcc with the PIC connected, it is switching off slower, clearly the 10µF on the PGA2310 main board gets charged by the programmer, is this a problem?
2) When powered off, all pins of the ICSP header on the programmer are isolated, but with power on (12.5V, 78L12 regulator of the programmer bridged), the pins GND, RB6 and RB7 measure a short and seem connected, maybe the 7406 is broken or what?

Has someone built this preamp and managed to bring the code up with ICSP?

Thanks & kind regards,
Lukas