There are no USB modules compiled for Alpha. The installer correctly detects the usbi host controller and the kernel attempts to load the USB module on reboot, but it doesn't exist. I recompiled with USB support and the module insert and found the USB controller. This was on a system type Nautilus.
This will be alleviated somewhat with kudzu-0.72-5/0.78-1, because it will not configure the USB controller to be loaded if there are no modules.
Why not actually build the USB modules?
*** Bug 17768 has been marked as a duplicate of this bug. ***
USB modules are included in the 2.2.17-4 kernel.