[avr-gcc-list] PonyProg 2000: Cannot read and write to device

[suzet war]

hi,
i think i'm having a big problem here.
hope anyone please help me. 

I'm using mcu=atmega8535, WinAVR compiler and PonyProg
2000 to upload the hex file into my mcu. for your
informations, i'm using AVR ISP connector (parallel
port)to download the hex file. Before this, i have
successfully upload the hex file into the mcu (i also
set the security and configurations bit).but after
6-10 times i read and write on/to the mcu device, now
it seems the PonyProg cannot read and write on/to my
mcu anymore. it keeps giving warning [Device missing
or unknown device (-24)]. why is this so? 

i hope anyone could help me, as soon as possible.

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