Installation Troubleshooting
From ArchWiki
Introduction
There are some problems that can occur while running the install media that prevent proper installation of Arch Linux onto your machine. If your error is listed here, try the solution indicated. Otherwise, ask on the forums or the arch-general e-mail list.
Problems
Q: "The keyboard becomes unresponsive and the mouse also stops working."
A: Try editing the kernel parameters. Reboot your computer, and at the GRUB (boot) menu, instead of selecting "Install", navigate there and press "e". Go to the line that starts with "kernel" and press "e" again. Try adding one or both of "noapic" and "acpi=off". Also, check to see if your system BIOS has an available upgrade - this problem can often be caused be an old BIOS.
Note: The installer does not have a graphical user interface, and therefore your mouse will not work anyway. The error was noted with a USB mouse, so its status as "on" or "off" was discernible.
Note: Taken from http://bugs.archlinux.org/task/13390?project=6