Finally found it .... yep .... my mistake. I use 1 ohm resistors as bridges on the circuit board and one was used for the reset of the programmer to the Mega644. But I placed a resistor of 1k .... stupid huh!!! This resistor in series with the pull up of 1K makes it in fact a voltage divider by two and so the chip never saw the logic zero to be programmed then. Strange enough , my logic probe DID see the logic zero so I didn't pay attention to it.
Secondly , as the programming worked fine but now and then , when programming the fuse bits , there still happed something wrong what sometimes made the chip unusable. So I had to clear it again with the Leaper48. What I changed now is the pull up resistor of 1K for the reset circuit , I placed now a 10K resistor and for the moment , it works perfect , even when I'm "playing" with the fuse-bits. Mark , thanks for your patience and help .... I hope this won't happen again.
Greetings to you all !!
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