Quick search icon spins forever after upgrading from 4.4 to 4.5
Since you're using multi-site Drupal, check the Image Upload URL in Civi to be sure it's not set to https://[domain]/sites/default/files/civicrm/persist/contribute/. In a multi-site setup there is no such thing as a 'default' site.

The quickest way to determine if this is your problem is to visit the CiviCRM dashboard and check the browser console for a 404 error on arrow.png. You will notice that the URL to the png file starts with https://[domain]/undefinedpackages/. Or try to use an ajax-powered feature and receive a JS error like "'back' is undefined".