call to serverside func fails

Call to serveside function returns "NetConnection.Call.Failed Failed to execute method".
I read livedoc thousands times and have no clue. Since main.asc loads another asc for components and
this asc is uneditable, I have to make this server-side func using Client.prototype.
Any tips from you fms developers who have gone thru this would be much appreciated!!!

My codes look like this:

Client-side:
this.nc("deleteFiles", new Res(), fileID);

Server-side:
load("uneditable.asc");

Client.prototype.deleteFiles = function(fileID){
...// codes to delete files on server
};