Ubuntu used a patch for this, but it's just a work-around for now and multiple upstream's developers told me that is not the right approach to use. -- debbug#555134 ...
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ID Status Resolution Sev Product Comp Assignee Reporter Summary
26163 NEW --- nor Sisyphus xfce-uti sem viy add /usr/share/xfce4 to $XDG_DATA_DIRS in /usr/bin/startxfce4

File a new bug in the "xfce-utils" component of the "Sisyphus" product