This is just a guess but are you trying this within your company's network and there is a firewall which requires authentication to access the internet? The part of the error which caught my eye is: Invalid proxy response status: 407 Proxy Authentication Required
This could be due to your proxy setup within your company's network. If you possible you might try on an open internet connection to trouble shoot. Otherwise you might need to configure the proxy settings in Eclipse to match the requirements of your company's network.