That's sad
What I tried so far is to map an 'echo "something" > /home/linuxme/bla.txt' to one of the mouse buttons so everytime I hit that button there's a new line with "something" in the file. After activating the Orbiter and pressing the button several times there are no lines added to the file. My guess is, that Orbiter itself captures the mouse button events before xbindkeys does. Maybe there's a way to run xbindkeys with higher priority or whatever to be the first application to captere the events, but I don't know how.
I only wonder why this problem is not reported more often, as there must be a lot of people using their more-than-three-button-mouses with linuxmce instead of a gyromouse, or am I wrong? Btw.: how are the three extra buttons on the gyro mouse mapped to the menu functions?