Allen, I think we're talking about the public site editor not "internal" site pages - and it still relies on a right click context menu. The editor is known to be very buggy and many features are broken or only work intermittently unfortunately. Not sure if it helps, but in Firefox the context menu you want is "hidden" under another menu and can be opened if you click "underneath" the top menu and hold the mouse button till it's revealed.
It seems to work ok in IE8 so perhaps you can also try compatibility view for the editor urls.
