If you're connected to the internet via a proxy server, confirm that Internet Explorer's proxy settings are configured correctly.
Also ensure you have checked Library > Settings > Use IE's Proxy Settings
Our products will use IE's proxy settings even if Internet Explorer is not your default browser.
If you're behind a proxy server, your settings are usually obtained from your IT admin or provided by the proxy server.
It is possible that your machine has been configured NOT to use the IE settings by default for .NET applications.
In the applications install folder there is file with a .config file extensions.
Edit this file and add the following after the closing system.data tag and before the closing configuration tag. This will force the application to use the default IE proxy settings overriding the machines configuration.
If that does not work then the following will explicitly define the proxy settings
If the proxy server requires authentication then this will use the default credentials:
For more information: http://support.microsoft.com/kb/318140