Sqldependency error

Hi,

I'm executing a command with "Select Col1, Col2 from dbo.Table" query. SqlCommand has SqlDependency attached. 

After I open the SqlConnection and call SqlCommand.ExecuteNonQuery(), I get following message in eventlog (at every second):

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An exception occurred while enqueueing a message in the target queue. Error: 15404, State: 19. Could not obtain information about Windows NT group/user 'doman\accountname', error code 0x5.

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If I'm logged in as local administrator account then also I receive the same above error in event log.

Following are the few settings changed in the database, but have found solution:

- Service broker is enabled from Database Properties > Options Tab.

- LogOn user of SqlServer database service is changed from default (Network Services) to local administrator account.

I wanted to know:

- What does the above error message indicate? 

- If SqlDependency object is created under local administrator login then why is the doman login used to create Service Broker Queue?

Thanks.