I’m posting this because there’s not a lot of support from WD that I could find on this, if any at all.
This morning I upgraded the RAM in my iMac. This obviously meant ejecting external drives, including Thunderbolt My Book and Velociraptor, and disconnecting them from the Mac. When I finished the RAM upgrade and reconnected everything and powered up my Mac, while other external drives would power up and display in Finder (and Disc Utility), the two Thunderbolts would not.
Eventually I discovered the solution was a very simple one, basically I disconnected all cables, including power, from both the drives and plugs and then set them both up again as if they were new, i.e.: 1/ connect power jack to the Thunderbolt, 2/ plug into powerpoint and turn on, 3/ connect Thunderbolt cable to drive and finally, 4/ connect Thunderbolt cable to the Mac. All of this was done while my Mac was on by the way.
Both Thunderbolts were back in the Finder (and Disc Utility) and equally important, no files/folders appear lost or damaged.
Hope this helps someone out.
