I have searched these forums and many others for a solution but have not found anything that helps. I have a 1tb WD MyBook that will not mount on my iMac through firewire, but works with usb. I have tried connecting it to my macbook with firewire, and it works. Also works on another iMac I tried, just not on mine. That led me to believe the ports were bad on my iMac. I tested a few other firewire devices, and they all worked. So the drive is in working condition, and so are the ports on the mac. I have tried resetting the pram, turning off and unplugging all components and letting it sit for 25-30 mins, repairing disks, different firewire cables, even tried a firewire 400 to 800 adapter. Nothing works. Then, I decided to try something different. Seeing as there are two FW ports on the back of the drive, I ran one cable to my iMac, and another cable to my macbook. Finally, the drive shows up on my iMac. Once I got it working, I unplugged the cable from the drive to my macbook, and it locked up the drive. I can't read/write onto it. But when I plug the cable from the drive back into the macbook, it works again. Why do I need it connecting to two different computers to get it to show up on my iMac? Is it a power issue? Before, it just said 'Unknown device' in System Profiler. When it's connected, it shows both macbook and mybook. As I said, I've looked everywhere for an answer but I don't know why it's doing this. Any help is appreciated.