scrolling with wheel mouse

[Adam Hardy <adam.ant@cyberspaceroad.com>]

I rebooted 1/2 an hour ago and when x came back and I started using the mouse, I 
realised the wheel on the mouse wasnt scrolling anything.

This is on etch.

I honestly don't think I installed or upgraded anything that would have caused 
this, and I'm at a loss for what to do. This is my config in /etc/X11/xorg.conf 
which hasn't changed recently at all:

Section "InputDevice"
    Identifier     "Configured Mouse"
    Driver         "mouse"
    Option         "CorePointer"
    Option         "Device" "/dev/psaux"
    Option         "Protocol" "ExplorerPS/2"
    Option         "Emulate3Buttons" "true"
    Option         "ZAxisMapping" "4 5"
    Option         "Buttons" "5"
EndSection


I've spent the last half an hour trying to track down the problem.

What happened? How can I get scrolling back?

I'd appreciate any help.

Adam