Hi,
As you know that the KM34Z256 has only one flash module, when you are operating the flash for example erasing/programming flash, the code to operate flash must be located at RAM and execute from RAM, secondly, you can not execute any code in flash, if you put the vector table in flash and put the ISR in flash, you have to disable interrupt, after the flash operating complete, enable interrupt.
If you want to enable interrupt while you operate flash, the interrupt vector table must be copied to RAM and modify the Vector Table Offset Register, thirdly, you have to put all ISR in RAM by copying the ISR from flash to RAM.
Hope it can help you
BR
XiangJun Rong