Robert,
There is no error in the code. However, when I execute it from Flash Builder (even with the modifications you suggested), I still get no output. I assume the output layer of the buffer operation should be in the arcgisjobs (the output of the GP server defined with ArcGIS Server manager).
Another thing; tha service task url contains space, do you think that causes a problem? see code in attached figure.
Thanks,
Tarek