Keyboard and Mouse Woes

When I boot the OSX install DVD with iBoot, everything works fine until I get to the language select screen. There, I find that I can't move my mouse, and my keyboard doesn't even seem to be on (yes, it is plugged in). When I disable legacy USB support in the Bios, my keyboard doesn't work in iBoot, and iBoot doesn't recognize my USB dongle that contains one of my OSX installs.

Specs:
CPU: Core 2 Duo E6850 @ 3.00GHZ
Motherboard: DP35DP Intel Desktop Board
Keyboard: Microsoft Digital Media Pro Keyboard
Mouse: Kensington Pro Fit USB Wired Full-Size Mouse

Thanks for any help you can give!