SQLQueryNotificationStoredProcedure exception filling up the log

I'm seeing this exception over and over again for different users (exceptions seen via SQL Profiler).  Any idea/clues as to where these are coming from and why?

ExceptionThere is already an object named 'SqlQueryNotificationStoredProcedure-6b3cfc31-1210-44d0-9e9b-b049ec8d54f9' in the database.SqlQueryNotificationService-6b3cfc31-1210-44d0-9e9b-b049ec8d54f9