I didn't found a libxfcegui4 component so I put this in “general”.
Seems that xfce-exec still uses xftree4 instead of (for example) thunar.
Attached patch fixes the problem (it's against branches_4.4 but should apply cleanly on trunk).
Created attachment 1608
patch to cal thunar instead of xftree4
Adding Nick to CC: so this one can be fixed in 4.10.
Because this is seriously broken. ad30dd6