Ok I am having a weird problem. My Airport Extreme does not allow me to connect to an external hard drive (with its own power supply) formatted as MacOS Extended (with GUID partition scheme). When I plug in this hard drive to the airport extreme base station, it shows up in Airport Utility and I can see the hard drive in Finder. However, when I click on it, it asks me to specify the Airport Extreme password. When I type in the password, it says "Trouble connecting to server... Please contact System Administrator..." I have no trouble reading and writing to the hard drive if I plug it in directly to my macbook. Here is the funny bit. When I reformat the hard drive using Disk Utility as MS-DOS (FAT) and then plug it into my base station, I have no issues connecting to it! I am still asked to specify the password when I try and connect to it and this time, it shows me the content of the hard drive without issues. Have tried this multiple times and tried repowering the base station. Any ideas? I am using an Intel-based macbook running Snow Leopard (10.6.6).