Yesterday, I used software update to apply the 10.5.7 upgrade on my Mac Mini and, since then, I haven't been able to access a Buffalo external USB hard drive which has worked perfectly for the past couple of years on the same machine. I have tried the drive on a PowerBook still running 10.5.6 and all works fine so I know the drive is OK. I have also swapped cabling around so the drive connects directly to a USB port on the back of the Mac Mini rather than a USB hub but with no success. last night, having read advice on this forum, I downloaded the combo update for 10.5.7 and applied that in case something had gone wrong with the update. Sadly, still no joy. The drive doesn't appear in Finder, nor can I see it in 'Disk Utility'. lastly, I tried to see if it could be seen as a USB device in Profiler but it isn't there. I'm really hoping I am doing something really dumb but can anyone help me? I'm afraid I'm fast running short on technical expertise on OS X and am not even sure if I can 'downgrade' back to 10.5.6. All advice, tea and sympathy very gratefully received!