Comment 1 for bug 1066573

Duplicate of
Bug #775702 “Some menu icons missing in Inkscape since upgrade to 11.04”

This is a conflict with Unity's global menubar. You can launch inkscape from the terminal with this command to disable the global menu for Inkscape and verify that the icons are still there (unless desktop-wide disabled via gtk settings for all menus):
$ UBUNTU_MENUPROXY=0 inkscape