I have a new WD Cloud external drive on my home network, and am working on two iMacs. On both iMac's I cannot insert an image in a Thunderbird email or attach a file from that drive. When trying to do so, I can see the drive and it's folders, but they are all grayed out and inaccessible. I CAN insert images into Word on the iMacs from the same WD drive, and the files on it are fully accessible from Finder. Thunderbird on a Windows 7 laptop also successfully accesses files stored on the WD drive. I have "mapped" the drives on the iMacs per the WD instructions. Any clue as to how I can solve this? It's most frustrating. Thanks.