I got it working (marble mouse, ubu 11.04, chromium and firefox): 1. I installed gpointing-device-settings (appears in the gnome-control-panel as pointing device). Check middle-click if you like, then scroll wheel emulation with button 8 (= small left button). Check vertical scroll and validate. 2. Check that firefox is configured as stated here: http://www.ehow.com/how_7390615_do-logitech-marble-mouse-scrolling_.html

This article https://help.ubuntu.com/community/Logitech_Marblemouse_USB explain the button mapping (read first paragraph carefully)

Hello Francoise. I finally got a bunch of stuff sorted out. I am sometimes my own worst enemy. I didn't realize gpointing-device-settings even existed. I followed your instructions, let my software manager [Linux Mint 13 now] install this, and it's a perfect solution to my problem. Thank you very much for posting this, and my apologies for taking so long to commend you for your help.