Boot into basic terminal mode and run "pacman -Q|grep input". I recall having to specifically install keyboard and mouse drivers but that seems to have been replaced by something called "evdev".
In /etc/X11/xorg.conf I have this:
Code:
Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
EndSection
Section "InputDevice"
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/input/mice"
Option "ZAxisMapping" "4 5 6 7"
EndSection