In the past we have seen this assertion failure being called if there is a custom trigger that has the following line:
Set Nocount Off
If you run the following script it will show you all of the triggers on the database. You will need to review the triggers and make sure none of them contain the Set NoCount Off line.
Select * from sysobjects where xtype ='tr'
Then to review each trigger whose name begins with X (by convention a customized trigger should have a name starting with x) using this command:
sp_helptext xtriggername
Here is an example of how you would modify the trigger to Set NoCount On.
Example of how to set this to ON:
alter TRIGGER TrnsfrDocStatusUpdate ON TrnsfrDoc
FOR INSERT, UPDATE
AS
Set NOCOUNT ON