Duning Letter generate program completes in Error (SQL-02112 SELECT..INTO returns too many rows)

 Hi

  When we are trying to submit Dunning letter generate Program we are getting error message as below

 ps_process SQL-02112: SELECT..INTO returns too many rows                      
Program exited with error.
/oracle/11iappsSUPPORT6/support6appl/ar/11.5.0/bin/ARDLGP
Program exited with status 1

As Dunning Letter Generate is Spawned Program we are not able to indentify select sql where we are getting this error

if there is any way to identify this that will be of greate help

Thanks

Kamalakar.G