Fatal error: Class name must be a valid object or a string in /home/dsmedia/blog/public_html/includes/common.inc on line 7749 I installed a module in drupal called Views Media Browser, that is when I first noticed the issue.  

I properly uninstalled the module (unchecked it, uninstalled it, then removed the folder from my sites/all/modules folder).  Now when I go to any article content I've created I am welcomed to the above mentioned error.

I checked the file and the location of it mentioned in the error

/**
 * Get the entity controller class for an entity type.
 */
function entity_get_controller($entity_type) {
  $controllers = &amp;drupal_static(__FUNCTION__, array());
  if (!isset($controllers[$entity_type])) {
    $type_info = entity_get_info($entity_type);
    $class = $type_info['controller class'];
    $controllers[$entity_type] = new $class($entity_type);
  }
  return $controllers[$entity_type];
}


I even compared it to a vanilla version of Drupal and the files are the same. 

I noticed that it does not occur with basic pages or any other content type I have. I would prefer not to have to restart the site, so if there is a way to correct this fatal error I would appreciate it.
I had a similar issue today (same error message) and I just solved it. It concerns my personal case, but if the description can help anyone : 
the problem was the fact that I had created a few items with a content type that I deleted since. So these non published items had an invalid class, because the content type was not existing anymore. 
I found these 3 items in the list of content with a blank space instead of the content type name. 
Deleting these 3 items, and then extracting/importing the database again to the customer made it work. 

The stange thing is that my version of the site was still working since I deleted the content type, so I couldn't understand why suddenly this problem when migrating the site.