I am not able to use Dropbox > error Trouble connecting to Dropbox servers.

[net.gaurav]

please help, I am using ubuntu 13.04, I installed Dropbox and then I am not able to proceed further it is giving following error,
Trouble connecting to Dropbox servers. Maybe your internet connection is down, or you need to set your http_proxy environment variable.

[fantab]

The dropbox servers could be temporarily down...
Try changing the DNS server...
Do you use any third party 'host' blocking? If yes, then remove Dropbox from that.

[net.gaurav]

what is third party host blocking?

[fantab]

what is third party host blocking?

... if you have to ask then you don't need to worry about it.
More Info:
https://en.wikipedia.org/wiki/Hosts_%28file%29
http://winhelp2002.mvps.org/hosts.htm

From Terminal run the following command:

dropbox start -i

... and post the output here, if any Errors are reported.

Most likely its a temporary issue with dropbox servers. Try again after sometime.

[marco-parillo]

Another possibility...I was able to sync with DropBox (and U1) from home, but not from work. Could your network administrators be black-listing DropBox to conserve bandwidth or prevent data leaks?

[Johan De Cauwer]

This is what Dropbox itself says about the way the connection is made : https://www.dropbox.com/help/23/en and that means that if you can surf, especially hhtps like this link, you should be able to connect. I hope the link is useful. It is possible to block Dropbox, but it requires an effort...