Product Version = NetBeans IDE 7.3 Beta 2 (Build 201211062253)
Operating System = Windows 7 version 6.1 running on amd64
Java; VM; Vendor = 1.7.0_09
Runtime = Java HotSpot(TM) 64-Bit Server VM 23.5-b02

I'm working on a Symfony2 project.
This YAML file is correct:

(...)
services:
    bt.twig.common_bt_extension:
        class: %bt.twig.common_bt_extension.class%
        tags:
            - { name: twig.extension }
        arguments: [@service_container]
 
However, the editor reports an error on the line "- { name: twig.extension }". It says "ScannerException while scanning for the next token we had this found character @(64) that cannot start any token"