Dropbox icon missing from the Notification Panel
I installed Dropbox on my Xubuntu 14.04 machine and everything worked great for months, until suddenly the icon just disappeared.
The problem seems to be caused by a bug in an update (Bug #1546176). A work around until this is fixed is to add a line to ~/.dropbox-dist/dropboxd (user411778)
Change ~/.dropbox-dist/dropboxd to add export DBUS_SESSION_BUS_ADDRESS=””
PAR=$(dirname "$(readlink -f "$0")")
exec "$PAR/dropbox-lnx.x86-3.14.7/dropboxd" "$@"
Then restart the machine.