Index: wp-admin/includes/plugin.php
===================================================================
--- wp-admin/includes/plugin.php	(revision 8454)
+++ wp-admin/includes/plugin.php	(working copy)
@@ -304,14 +304,19 @@
 		return;
 	}
 
+	//Invalid is any plugin that is deactivated due to error.
+	$invalid = array(); 
+
 	// If a plugin file does not exist, remove it from the list of active
 	// plugins.
 	foreach ( $check_plugins as $check_plugin ) {
 		$result = validate_plugin($check_plugin);
 		if ( is_wp_error( $result ) ) {
+			$invalid[$check_plugin] = $result;
 			deactivate_plugins( $check_plugin, true);
 		}
 	}
+	return $invalid;
 }
 
 function validate_plugin($plugin) {
Index: wp-admin/plugins.php
===================================================================
--- wp-admin/plugins.php	(revision 8454)
+++ wp-admin/plugins.php	(working copy)
@@ -165,8 +165,10 @@
 $title = __('Manage Plugins');
 require_once('admin-header.php');
 
-validate_active_plugins();
-
+$invalid = validate_active_plugins();
+if( !empty($invalid) )
+	foreach($invalid as $plugin_file => $error)
+		echo '<div id="message" class="updated fade"><p>' . sprintf(__('The plugin <code>%s</code> has been <strong>deactivated</strong> due to <em>"%s"</em>.'), $plugin_file, $error->get_error_message()) . '</p></div>';
 ?>
 
 <?php if ( isset($_GET['error']) ) : ?>
Index: wp-settings.php
===================================================================
--- wp-settings.php	(revision 8454)
+++ wp-settings.php	(working copy)
@@ -417,7 +417,8 @@
 	$current_plugins = get_option('active_plugins');
 	if ( is_array($current_plugins) ) {
 		foreach ($current_plugins as $plugin) {
-			if ('' != $plugin && file_exists(WP_PLUGIN_DIR . '/' . $plugin))
+			if ( '' != $plugin && strpos('/' . $plugin, '/../') === false && strpos('\\' . $plugin, '\\..\\') === false
+			&& file_exists(WP_PLUGIN_DIR . '/' . $plugin) )
 				include_once(WP_PLUGIN_DIR . '/' . $plugin);
 		}
 	}