I nearly gave up in frustration after downloading Boot Camp, making the driver CD, printing out the instructions, and slipping in the XP Pro install disk and then having the installation freeze after just starting to install. I called AppleCare, asked the local certified tech, other Apple geeks, etc. who could not figure out what the problem was, and I even exchanged the system disks because the techs thought they must be defective.
Then, I remembered that -- because my desk was overloaded with the old and new towers, big LCD, and my printer was too far away from the tower -- I had plugged the printer into the keyboard to print the directions. I'd left it plugged in, and the Windows install gagged on the connection. In that moment of enlightenment, I unplugged the printer USB connection to the Apple keyboard, and the installation of XP Pro via Boot Camp went quickly and smooth as silk.
Nowhere did I notice in the instructions to be sure not to plug in anything via the keyboard USB, so it really threw me at first. Simple solution, at least. Moral of the story: Don't plug anything into your USB keyboard connection while installing Boot Camp/Windows!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070319133531742