Try installing udisks. I don't know how this program is started, so reboot and retry. At the moment, this is the most simple test I can suggest you to do. Otherwise I looked at a list given by the command line "apt-cache search nautilus" in case I could see one or several packages or plugins likely to help see your camera in the file manager, but I'm not sure which ones to suggest you. You could take a look too, and see what they describe, and decide on your own which ones to try.
When you launch "lsusb" as root with the camera plugged in and set to on, does lsusb see it ? And is the battery of the camera full enough ?