VELLEMAN PIC Programmer K8048/VM111 failed.

Hi,
I’m using VELLEMAN PIC Programmer K8048/VM111. And it programs a 16F628 properly for the first time.
But when I erase the code and wanted to re-write it again, an error appears.

Error:
Write Error at:0000
Wrote:292D
Read:0000
No amount of re-erasing (is that a word?!?!) helps, it's as if erasing the initial code has somehow killed the chip.
It recognizes its presence, but it fails to write anything to it.
Also the Device ID comes up as 3FFF, which it didn’t before.
Any idea what’s going on here?
Thanks in advance.
