Comment 116 for bug 260492

Once you have Nautilus open, e.g. by typing nautilus in a terminal, you can navigate to and right-click on any of the objects in your Places menu and choose "other application" etc. This made my folders open with Nautilus again, whether I do it from the Places menu, using GNOME Do, or from within Nautilus itself. If this doesn't work for you, I'm afraid I have no further advice. Anyway, this is just the same workaround mentioned in the original bug posting and I guess this bug is really about the hijacking of the opening application in the first place.