System.ArgumentException: The path is not of a legal form. How to fix it?

[Olivaras]

System.ArgumentException: The path is not of a legal form.
   at System.IO.Path.NormalizePath(String path, Boolean fullCheck, Int32 maxPathLength)
   at System.IO.Path.GetDirectoryName(String path)
   at Iros._7th.Workshop.Settings.<VerifySettings>d__2.MoveNext() in c:\Iros\7thWorkshop\Settings.cs:line 47
   at System.String.Join(String separator, IEnumerable`1 values)
   at Iros._7th.Workshop.fLibrary.fLibrary_Load(Object sender, EventArgs e) in c:\Iros\7thWorkshop\fLibrary.cs:line 120
   at System.Windows.Forms.Form.OnLoad(EventArgs e)
   at System.Windows.Forms.Form.OnCreateControl()
   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
   at System.Windows.Forms.Control.CreateControl()
   at System.Windows.Forms.Control.WmShowWindow(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.ContainerControl.WndProc(Message& m)
   at System.Windows.Forms.Form.WmShowWindow(Message& m)
   at System.Windows.Forms.Form.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

[EQ2Alyza]

Go read the 3rd question of the FAQ section in the written tutorial thread.