I'm new to all things Apple, and I did a search but did not find an answer that helped my situation. I bought an Airport Extreme base station with my new rMBP, then plugged in my USB 2TB WD external hard drive thinking I could get a decent NAS. After I set up the NAS, I was able to connect for a while. However, the next day when I tried to look or put something on the NAS, I could not see or access the drive. I get a message saying '"NAS" can't be opened because the original item can't be found'. When I physically look at the drive, it's still powered up. The only place I can "see" the drive is going through Airport Utility, and it just shows that it is there. I have file sharing with a disk password enabled. The disk is formatted Mac OS Extended, by the way. Any ideas for an OS X rookie?