ICSP reads different code each time

I’ve been reading, verifying and writing code to the 16f that came with the kit, but now ive swapped in a larger chip with existing code (18F458) that I am trying to “back up” before making modifications to it. The Velleman software doesnt cover the 18F458 so I’ve used Winpic, which also works flawlessly on the lesser controller, but it reads different code each time with the 18F and the code is not in one block, but scattered all throughout the buffers. It obviously never verifies.

Any ideas?

Dear sir,

This PIC is NOT supported by any of our software for our pic-programmers (progpic or picprog200x). We do not support any other used software.