GP Service run in REST and give error

Discussion created by francesco_81 on May 16, 2011
Latest reply on Apr 18, 2013 by deona
Hi guys,
i have develop a gp service and when i run the gp service in REST i have this error:

Unable to get value of param 'Output_Layer__2_' for Job ID 'j250539ef70ac48bba44b33ef6aca6f54'. The job may not exist or it could still be executing or could have failed.

Code: 500
What is this error?
help me please