If you are comfortable at the command line, there are ".desktop" files located in /usr/share/applications/hildon. They are are used to define the menu items availabe.
under the root account, the following seemed to work, as a permanent but reversable solution:
Browser Back/Forward buttons only avail on keyboard?
This seems a little silly.. It seems the + - on top would have been more ideal for full screen view. I hardly ever use the "zoom" function.
A app or something would be nice to reassign that button to volume , or navigation when needed.
# chmod 000 /usr/share/applications/hildon/rhapsody.desktop