Alert gets error

I have create alert in SQL server 2008 r2 (*64).But it gives me a error like below.

SQLServer Error: 512, Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression. [SQLSTATE 21000]

USE [msdb]
GO
EXEC msdb.dbo.sp_add_alert @name=N'My Test CPU Alert', 
    @message_id=0, 
    @severity=0, 
    @enabled=1, 
    @delay_between_responses=0, 
    @include_event_description_in=0, 
    @database_name=N'', 
    @notification_message=N'', 
    @event_description_keyword=N'', 
    @performance_condition=N'Resource Pool Stats|CPU usage %|default|=|5', 
    @wmi_namespace=N'', 
    @wmi_query=N'', 
    @job_id=N'00000000-0000-0000-0000-000000000000'
GO