Pete,

You already, probably, have done this but had to share that with you anyway.

There are times that the queues go down in case of some error what not..

Therefore, if that happens then one or more queues under MSDB.SERVICE BROKER.QUEUES.DBO.XXXX folder may have an arrow down so to speak ..

and sometimes a right click/enable might bring it back up online if the issue behind the scene were not critical..