We are using/teaching Lightroom in a community college setting. We have a lab with iMacs (10.8.5) running LR5 and another lab across campus with PCs (Windows 7) running LR5. Additionally, our students often use personal laptops of various platforms, many with windows 8. In order for students to use both labs since differing classes use differing systems, students purchase external hard drives that they format to FAT and on which they keep their LR5 catalog. The merely plug in and launch LR5 from their personal catalog on their drive. Since Lightroom 5 and Windows 8 many of our students are having problems going cross platform. They plug into an iMac, and all their pictures are missing, i.e. "!." The Folders panel shows the previous USB port directive from the last machine he or she used, "C:" "F:" etc.. Sometimes, you can right click and "Show Parent Folder" or "Find Missing Folder" successfully, to point LR in the right place, sometimes not. Sometimes the application freezes or the catalog quits and may even become corrupt. If you do get LR to recognize the files via "Show Parent Folder" or "Find Missing Folder," once you plug the external drive into a Windows machine, it starts all over. Sometimes, on a Windows platform, when locating a "missing" folder, Lightroom will say it already exists and ask to "Merge" the folder yet to only folder location is the one pointed to. Sometimes, for the sake of getting one image developed and printed, a student will seek to locate the missing file and "find nearby missing files." Usually the file can be located and quitting and restarting LR5 will also "find nearby missing files." What has changed that is causing some many issues. Is the software platform specific now? Is there some reason the drive letter path isn't being a dropped when going to an iMac or being reinstated when going back to the Windows machine? HELP!!