RFC Call terminates with RFC_ERROR_SYSTEM

RFC Call terminates with RFC_ERROR_SYSTEM_FAILURE: I want to use a function module that displays a screen (special searchhelp). Why does the Call terminate with an error message RFC_ERROR_SYSTEM_FAILURE ?

Use the -dialog option of the Call statement , e.g.

Call "FUNCTION_GET_MATERIAL" -dialog ...

GuiXT then uses a special RFC connection that is able to process screens.