99% of the time this is your firewall or proxy settings.
Check your firewall settings. It should not be blocking "Betting Assistant.exe" or "BA_Launcher.exe" from making outgoing connections.
If it's not your firewall then check your proxy settings. You could be using a proxy server that does not allow the connection to Betfair. See
http://support.microsoft.com/kb/135982 for an explanation of how to check your proxy settings.