I have had 5 calls since May for people with a KM45/5530 and erratic C0240.Most of the time they can be reset but other times I need to replace the machine Main or Printer pcb's when they start to occure more often.
As per Service Manual
The sucess that I have had with the Main pcb`s is 50/50 and those pcb`s came from older trade in`s. When the Main pcb did not fix 1, a new print system did till today
Im I missing some thing simple?

The error can be caused by an incorrect firmware update operation:

If you, after update, has pressed the "RESET" button that appears on the display and , switch-OFF the machine the error code C-240 is shown after reboot.

Update procedure: Just Switch-OFF with out pressing the "RESET" button..

Procedure if C-240 is still displayed:

Try to upload the firmware again. If it doesn’t help it's necessary reprogramm the Printer DIMM

Printer pwb error. If you have any additional memory you should also remove them as this can also give this error. If still fails you should reprogramme the print system DIMM firmware , though you need the appropriate equipment.

Something else to check for - a poison printer hard disk.

I had the same FS-8000c blow a main pcb twice in a couple of weeks, then the loaner KM-C830 with print system P that we brought out popped a c-0240 immediately after being turned on in the customer's location. It was working fine in our showroom, but I did remove the print hard disk from the printer and put it into the C830 so the print driver didn't need to be altered. That was the only thing in common between the machines. Now I have a junk print system P also. That has been one expensive hard disk.

Yes, have this prob on 3035 print/scan sys. Constant C-240 flashed machine according to specs, (special procedure) for 146.07 you must follow it EXACTLY! Upgrade the machine and NIC cards also. Other causes, print board itself, print driver (try using mini driver), parallel cable with jet direct box. The later is the prob I still have, we are trying to go direct thru CAT5 w/ a linux program.