atmega32 notdetected

[benji]

i did use this micro a lot (been re programmed more than 50 times)
and i did program it 2 days ago to send data strings serially (uart) at 1200 baud rate
i did use this micro for about half an hour then i wanted to change the program
the serial programmer couldnt see it anymore ,,buff (error -24 in ponyprog)
i did check the programmer with an atmega8 and it worked, so the problem isnt in the programmer.
the mega32 still works with the same old program on it,but can not be programmed again.

plus: i didnt mess with the fuses or security bits.

any clue?