I've tried editing the /etc/X11/xorg.conf, I've tried xmodmap -e "pointer = 3 2 1 4 5 7 8 9 10 11 12" and neither works.
SuSe control center isn't of much help either.

Anyone have any idea what to do?

I use a MS Wheel Mouse Optical (USB). Computer is Compaq EVO n600c.

My /etc/X11/xorg.conf (mouse related part) looks like this:

Section "InputDevice"
Driver "synaptics"
Identifier "Mouse[1]"
Option "ButtonNumber" "5"
Option "Device" "/dev/mouse"
Option "InputFashion" "Mouse"
Option "Name" "Synaptics;Touchpad"
Option "Protocol" "imps/2"
Option "SHMConfig" "on"
Option "Vendor" "Sysp"
Option "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
Driver "mouse"
Identifier "Mouse[3]"
Option "Buttons" "5"
Option "Device" "/dev/input/mice"
Option "InputFashion" "Mouse"
Option "Name" "USB-Mouse;ExplorerPS/2 on USB"
Option "Protocol" "ExplorerPS/2"
Option "ZAxisMapping" "4 5"
EndSection

Any help much appreciated.

I solved it by deleting the touchpad config using SaX2 and then restarted the computer. The SuSE control center will then work when changing the mouse from right to left hand.

Big thanks to BandiPat!