Comment 70 for bug 260492

I had the same issue after a fresh install of Intrepid while re-using my /home

$ cat .local/share/applications/mimeapps.list
[Added Associations]
text/html=epiphany.desktop;firefox.desktop;
application/x-executable=userapp-bless-QAFMEU.desktop;
application/x-extension-Ora=gnochm.desktop;
application/x-extension-Orb=gnochm.desktop;
application/x-extension-Pra=gnochm.desktop;
application/octet-stream=gnochm.desktop;
application/x-extension-Hig=gnochm.desktop;
application/vnd.rn-realmedia=realplay.desktop;
text/x-csharp=gedit.desktop;
inode/directory=mplayer.desktop;

So, mplayer was called. When I uninstalled mplayer, it was defaulting back to standard behaviour (nautilus)
issue fixed by editing .local/share/applications/mimeapps.list
and changing :
inode/directory=mplayer.desktop;
to
inode/directory=nautilus-folder-handler.desktop;