Are you by any chance connected to a VPN or internalnetwork? Commonly, this issue appears when this type of connection is being used.
If this doesn’t solve the issue, you can try downloading the Arduino IDE 1.6.0 which already comes with the Edison and Galileo packages pre-installed, https://downloadcenter.intel.com/download/24355/Intel-Arduino-IDE-1-6-0.
I do not think this is the problem here. I set correctly the proxy settings in the Arduino IDE. Furthermore the Board Manager is able to download update infos before installing the INTEL Edison.
The URL that the Arduino IDE 1.6.4 is fetching does not exist anymore...
So I already workaround by installing the Arduino IDE 1.6.5 and here no problem.
Could you please by the way give the valid URL Address to locate the INTEL Edison Board package ? so that it can be easily fixed without the need and extra time to re install a new Arduino IDE ?