I downloaded and installed the the OS X Mavericks update and now, my macbook won't read my external hard drive anymore. It shows up in the disk utility and I clicked Verify Disk, and Repair, and it seems that nothing is wrong with it. No errors appear in the log. When I click Mount, it tells me that it can't mount it and to use the First Aid options. I've tried Ejecting and Mounting and replugging the device in, but still no luck. What can I do?