Warning: in_array() expects parameter 2 to be array, string given in _drupal_http_use_proxy() (line 1100 of /var/www/html/includes/common.inc)
This is the code for _drupal_http_use_proxy

function _drupal_http_use_proxy($host) {
  $proxy_exceptions = variable_get('proxy_exceptions', array('localhost', '127.0.0.1'));
  return !in_array(strtolower($host), $proxy_exceptions, TRUE);
}


The status message warns that $proxy_exceptions is not an array.

You can configure this setting on your settings.php file, this way:

$conf['proxy_exceptions'] = array('127.0.0.1', 'localhost');


Have you changed this variable to anything other than an array?

 $conf['proxy_exceptions'] = '127.0.0.1'; // For example


Maybe there is a contributed module which do this...

Try to insert a dpm on $proxy_exceptions or execute this on /devel/php  to show the value of this variable:

dpm(variable_get('proxy_exceptions'));


If you want to reset this variable:

variable_set('proxy_exceptions', array());


or

variable_del('proxy_exceptions');