uberOptions

Install my uberOptions pack to change the device settings for SetPoint! All it took was editing some XML files.

Since the Forward/Back actions use Application Specific settings on those buttons to send different events depending on what exe has focus, the fix I'm using only works for the default two buttons. If you want to do Forward/Back in Firefox/Opera 8 on another button (or reversed for that matter), use the "Keystroke" action with "Alt Right"/"Alt Left".
Since you can set any button to any action, you can easily end up without a left-click button, so be careful. If you do this; press Esc to cancel, use another mouse to fix it, or kill KEM.exe/Setpoint.exe in Task Manager with the keyboard. (Ctrl Shift Esc opens the Task Manager.)
These modified files work with SetPoint 2.22 - 4.80 (and probably later versions, too - but not the special "SetPoint 5.0/5.1/5.2" for the G9/G9x mice). If you are using an older version of SetPoint, install the newest available version (4.80) from Logitech's support site or FTP first.
Works with SetPoint 32-bit and 64-bit for Windows XP/XP x64, Windows Vista 32bit/x64, Windows 7 32bit/x64. My main computer now runs Windows 7 x64, so tell me if you have problems with other OS versions.