Atmega168 bootloader internal 8Mhz

Hello. I'm new on ARDUINO but with a lot of experience in SHARK, FPGA and others. I has a KK V2 board with ATMEGA168PA without external oscillator. I program is using USBasp ISP programmer and eXrteme Burner as burinig program. Now what happens I burn the file "ATmegaBOOT_168.hex" and everything was OK. After I burn also the fuses values with values that eXrteme Burner generate them (it has a window that you define the internal RC oscillator frequency and so on) the processor "disappear". The burning program can't connect to the processor, cant read the internal FLASH or anything else.
So what happens and what can be done now ? Somebody can explain ?