Comment 10 for bug 775640

mmc (martin-campbell) wrote :

If you want to simply fix the opening of files but retain XFCE/exo you can simply open "exo-preferred-applications" and change the preffered "file manager" under "utilities" back to "Thunar"

I'm guessing the install of XFCE changes this default, anyway flipping it back to thunar certainly fixes the behaviour in Unity for me.