I have just build the P16PRO40 and am using WinICProg to program my
PIC.

I tried posting this message on the winicprog site but there seems to
be a problem with the registration process.

I have tried toggling the button in the hardware setting and I get the
following:

vpp on: MCLR = 12.85V
clock high: PGC = 4.9V
output high: PGD = 4.5V

I'm using the circuit from www.olimex.com/dev/pdf/pic-pg3b.pdf

When I program the chip it fails on a verify. It does seem to program
something as the first few bytes are written although incorrect values.
I can then erase the device and reprogram it, and different bytes get
written to the start.

any idea where I can start looking? I've checked the supply voltage
with a scope and its stable.