I have an Apple Airport Extreme for wi-fi. I have several Macbooks and a Mac Mini sharing that wi-fi signal. I have an external hard drive connected to the Mac Mini, and I have been sharing that external hard drive via the Sharing preferences. I have Time Machine on the MacBooks backing up to that external hard drive, etc. However, in the last 48 hours, the external hard drive is no longer visible to the MacBooks. I've shut down and rebooted the Mac Mini multiple times. I've gone into Sharing preferences on the Mac Mini and it shows the external hard drive is being shared. But none of the other Macs can see the external hard drive. If you have a solution, or think you might be able to help, please email or call me. Thanks. Jeff Jeff Rutherford 413-475-0087 jeff at jeffrutherford.com