To recreate the issue, go to Manage extensions page and click on 'Add new' tab, you will see this message (see attached screenshot):
"There are no extensions to display. Please click "Refresh" to update information about available extensions."
We are seeing this issue in all of our CiviCRM 4.6.x installations. We did some digging in the code and debugged the code in CRM/Extension/Browser.php Line num. 246:
$url = $this->getRepositoryUrl() . $this->indexPath;
The value of $url comes up as - https://civicrm.org/extdir/ver=4.6.14%7CCcms=Drupal/single
If we go to this URL, we are seeing "The website encountered an unexpected error. Please try again later."
We could not replicate it on the prior versions and it seems there are some significant code changes in 4.6.x