If you insisted upon downloading Dropbox for Debian from their website, which was a very bad idea in the first place...

Install from the Dropbox website, then:

dropbox stop && dbus-launch dropbox start

on Lubuntu go to

Start/Preferences/Default applications for LXSession

In the Autostart section, Manual autostarted applications, copy/paste:

dbus-launch dropbox start -i

then hit "+ Add"

and reboot

The following doesn't work in Xubuntu! Damned if I know why.  Maybe this command runs before dropbox starts in the first place, who knows?

on Xubuntu go to
Start/Session and Startup/Add
name and description your choice
dropbox stop && dbus-launch dropbox start

So now I tried to gedit the rc.local file to autorun on startup:
sudo apt-get install gedit
sudo gedit /etc/init.d/rc.local
add this line right above "exit 0" very near the bottom
sleep 30; dropbox stop && dbus-launch dropbox start
save
reboot

And now this didn't work either. Running out of patience.

Ok, trying this:

Open terminal.
dropbox stop
sudo gedit /usr/bin/dropbox
Create a new line after "import os" and add the following:
os.environ['DBUS_SESSION_BUS_ADDRESS'] = ""
Save and restart

Success lives here!