geometry can not have z value

Hi
I have a model that generate a 3d line by this steps: user draw a line, then model calculate 3d line from a DEM file.

Everything is ok in my model and I can run geoprocessing service by .Net web application, but when I run my geoprocessing service by flex viewer 3, it return this error:esriJob failed

I checked service log file and found this error message:
geometry can not have z value

Please help me.
Regards