Comms problem

Hi again guys, I have another problem.The machine I am working on runs QNX4 but for some reason the floppy drive will not work. when you try to access the disc in either dos mode or qnx mode the drive light comes on and stays on locking up the machine even though a QNX boot disc works perfectly.
Also the dnc communications will not talk to an external computer even though when you short out transmit and receive on the machine end you get test ok. All the baud rate etc are set correctly and two computers have been tried. All you get is test received but no reply and then time out. Could this be some kind of security issue ? Regards Dave