Before you replace expensive PCBs...
First you need to check firewire card in your PC, or replace it (the best is with Texas Instruments main chip... its not expensive) also check firewire cabel...
While checking this - please switch off both - computer and printer, this is very important, because printer firewire pcb is very sensitive device....
Several times we had the same - but the printer continue work leaving white /blank/ stripes....
We have too HOT inside printroom, since we install air conditioner - problem not occured any more.
tom.