I have an external hard drive that has 2 forms of connection, USB2 and Firewire 800. It has worked flawlessly for about 1 year , now when connected to any Mac computer , desktop or laptop , with either connection , it does not register on the decktop . I have tried both USB2 and the firewire connections , restarts .... every form or combination. Any suggestions as the hard drive is my backup and and in many cases the only copy of much of my files. How to make the external drive readable ????