1.7.0 Update Collection Could Not Open http:/www.joomla.org/update/core/list.xml

From Joomla! Documentation

The Joomla Updater uses the php fopen command.

Those php configurations without fopen enabled will error with the following messages:

Update: :Collection: Could not update http://www.joomla.org/update/core/list.xml

Update: :Collection: Could not update http://www.joomla.org/update/jed/list.xml

You will not be able to use the Updater without enabling fopen for PHP. This is a web hosting issue.