I use LR on a laptop and a desktop, both Macs running Yosemite. I use the same external drive to store my LR photo catalogs and move it back and forth between computers. If I import pictures on one computer I get a "file access denied" when in the Develop mode on the other computer. In other words, I can only use the Develop mode on the computer where the original download from my camera occurred. I cannot find a solution and would appreciate any help. I am running the latest versions of LR and OS X. Thanks.