Either this is a Leopard problem or Airport Extreme problem, but when I have a printer and two external hard drives connected via a USB hub, only one hard drive will mount. I go to Finder, click on my router name and it shows both available hard drives. If I click on one, it'll mount that, and then I won't be able to access the 2nd. This problem disappears if I unplug the printer from the USB hub. Anyone else experience this, or know of a possible solution?