Duplicate Mouse Button Mapping

[ganderatc]

I have a Logitech mouse with back and forward buttons on it. Before I upgraded to Xorg 1.5, one of the buttons was essentially a 2nd middle click button. Now, the mouse has what should be the desired behavior, but I've gotten used to it being the other way. Xmodmap gripes at me when I try to remap them because it won't allow two buttons to be assigned to the same X events. Any ideas how I can get this back to the way it was?