intermittent "arm board not detected"

[spiyda]

Someone has asked me if I know the possible reasons for a problem with their vacuum pump intermittently stopping and then a message coming up with “arm board not detected” when a job is loaded in rvplace. ( I think he is registering on the forum )

Oddly enough last week I had a similar issue..  at the end of a long run of placing ( lonfg for me, about 5-6000 components)
 "arm board not detected" followed by "z axis switch not found", happened several times.. ( I then changed the "Z" axis switch, but haven't run it since)

What are the most likely causes of the "arm not detected" error?

[Mike]

Probably RS232 port issues, as the arm board is read via the serial port.
Try the armtest program - this continually reads from the sensors - run this and systematically wiggle cables. 
If your machine uses serial ports on the DSP carrier card it could be there as well, and maybe also the power supply to the arm PCB