Hi,
This means that the handler for the request is configured as fastcgi module which is supposed to run the fastcgi client as specified by scriptProcessor property but an entry for this fastcgi client is not found under system.webServer/fastCgi section. Easiest way to fix this would be to delete the handle in UI and add it again. Handlers UI will create an entry for scriptProcessor in the fastcgi section in addition to creating the handlers entry.
Hope this helps.
Kanwal