I've been trying to get my seven button (with scrollwheel) mouse to recognize my side buttons. I've implemented the scrolling in the wheel:

Option "Buttons" "7"
Option "ZAxisMapping" "4 5"

that works well. Then I downloaded and installed imwheel, and put this in ~/.imwheelrc:

".*"
None, Up, Alt_L|Left
None, Down, Alt_L|Right

It works if I map it to the wheel, but it completely ignores it if I map it to my side-buttons. I'm using a "Micro Innovations" optical wireless mouse, compatible with the IMPS/2 protocol. Has anyone seen this problem before?