Problem:

Slow responses from "Install from web" service mean that user is blocked from other actions waiting for the ajax to reply and render.

Steps to reproduce:

1) Install "Install from web" extension /administrator/index.php?option=com_installer&view=install

2) Wait for the Joomla service to be slow to respond... or fake it

3) Load the /administrator/index.php?option=com_installer&view=install page, and assume you dont want to install from web, you want to work with another of the tabs, click that tab

4) Note the loading throbber overlay prevents you from your quick and speedy workflow until the "Install from web" html loads from the ajax request

To fix:

Ensure that the preventative loading overlay only overlays the one tab content and not the whole page