I have Icecat 3.6.15 on Zenwalk 7 (2.6.37.4), with XFCE 4.8.0
This is 100% repeatable. Adding the 'new tab' icon to the toolbar next to the 'home' icon only works for the current session. Upon closing the app and repopening, the icon is gone and must be added again.
-- http://gnuzilla.gnu.org
