Hope someone can help.I got my new imac running leopard.I was using my WD 500GB external HDD as my backup disk for time machine etc and was working great till a few days ago. Now,when I connect(with firewire 800)- it does seem to start up but does not appear on the desk top.This happens with the USB connection as well.I first noticed the problem when time machine icon(clock) just kept rotating as if backing up,but it just kept going. this happened several times,so I restarted the imac,plugged/unplugged the WD without any joy. Now it does not even recognise it or appear on the desktop. I have checked the obvious->connections etc and all seem ok. I connected the WD to my ibook running 'panther-10.3' and it recognises it(via usb),so I presume the WD is working.I also connected another external HDD  and it seemed to work and be recognised on my imac. Not sure what to do next,not really keen on trying a complete new reinstall just yet,and that may even not solve my problem. Otherwise the imac seems to be working all right without the WD connected to it. 


PS-not sure if updating to 10.5.8 has anything to do with it,but the problem seems to have started may be 2-3 days after updating
grateful for any advice
thanks