Hooking up MacMini, miniStack v2.5, and M-Audio FireWire 410

I'm having a heck of a time trying to configure this setup. I'm a newbie to Macs. If I hook up the 410 directly to the Mini, everything's fine, but that means I have no external drive. If I hook up the external drive by firewire, and attach the 410 to the external drive (stack), the 410 won't "hook up", won't sync with the Pro-Tools, just keeps blinking blue. Please, if somebody could give me some idea of what I'm doing wrong? I've tried the keylock in the Mini and then the stack, but it doesn't seem to make any difference. Any help would be greatly appreciated!