Unable to restart Nautilus (required by Dropbox)
Try
sudo nautilus -q
or install a newer Nautilus for 14.04/13.10 from here
EDIT: What I forgot, after installing Nautilus 3.12, you will have to reboot -> sudo reboot
Report back if it worked ;)
I hope your problem has been resolved, if not this may help. I was also facing the same problem and this helped me.
Download the .deb file of Dropbox from here on the dropbox.com site.
Then after download, right click and select Open with software install.
Then install it.
Start drop box and you will get little dropbox icon on top right.
Reference