The only solution that solved my problem was to add the following line in this file '/home/user/.bash_profile':
sh ~/.dropbox-dist/dropboxd & thanks a lot -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To post to this group, send email to firstname.lastname@example.org. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/cd5e3176-9473-4038-957b-091df97196bb%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.