It's sounds like your web browser uses a proxy, but you didn't tell PPM about it. The docs mention setting the environment var HTTP_proxy to the URL of the proxy. In addition, it apparently checks for values in env vars HTTP_proxy_user and HTTP_proxy_pass. Set these if the proxy requires authentication.

Update: bah, the other post didn't use to say how to configure PPM to use the proxy. This post is rather redundant now.