Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 5496)
+++ wp-includes/functions.php	(working copy)
@@ -322,7 +322,7 @@
 	}
 
 	$notoptions = wp_cache_get('notoptions', 'options');
-	if ( isset($notoptions[$option_name]) ) {
+	if ( is_array($notoptions) && isset($notoptions[$option_name]) ) {
 		unset($notoptions[$option_name]);
 		wp_cache_set('notoptions', $notoptions, 'options');
 	}
@@ -356,7 +356,7 @@
 
 	// Make sure the option doesn't already exist we can check the cache before we ask for a db query
 	$notoptions = wp_cache_get('notoptions', 'options');
-	if ( isset($notoptions[$name]) ) {
+	if ( is_array($notoptions) && isset($notoptions[$name]) ) {
 		unset($notoptions[$name]);
 		wp_cache_set('notoptions', $notoptions, 'options');
 	} elseif ( false !== get_option($name) ) {