Is is so that by mistake if i had write fuse bit for External RC oscillator and in board i only have external crystal then i can not re-write fuse bit for atmega88 until i connect it with external rc oscillator? Because i have already facing the problem that if i write this fuse bits as External RC then i am unable to re-write the fuse bit. I have tried this for another IC also. When i write fuse bit, it is not even connecting to my AVR mkII ISP programmer. In other board I have to use internal RC osc, but I have written fuse bit to external Crystal, after that ic could not connect to mkII. Is there any point that I am missing. Is there any way to save my IC?