Index: wp-admin/includes/image.php
===================================================================
--- wp-admin/includes/image.php	(revision 5852)
+++ wp-admin/includes/image.php	(working copy)
@@ -91,6 +91,8 @@
 				}
 			}
 
+			imagedestroy( $thumbnail ); // Free up memory
+
 		}
 	} else {
 		$error = __( 'File not found' );