Almost always, this problem is caused by a personal firewall running on your computer (Kaspersky, ZoneAlarm,...) which blocks connections of JonDo. Please release JonDo in the firewall options or shut down the firewall.

If you are forced to use a proxy, please check in the network settings of JonDo whether you have entered the right address and, if applicable, the correct login name for the proxy. If the settings are correct, maybe your proxy operator blocks the connection to JonDonym.

Moreover, it is possible that you provider or network administrator block the connection of JonDo. Ask you administrator, or change you provider in order to solve this problem.

You might also use an outdated JonDo version. In this case, please update to the current version.