New Post: Error after change Task Settings

I'm using SharpDevelop or MonoDevelop
I've got an error after change option in ComboBox (If task is already running, then the following rule applies) in Settings tab.
Could You help me with this issue?

Microsoft.Win32.TaskScheduler.TaskPropertiesControl.taskMultInstCombo_SelectedIndexChanged (sender={System.Windows.Forms.ComboBox, Items.Count: 4}, e={System.EventArgs}) in 
System.Windows.Forms.ComboBox.OnSelectedIndexChanged (e={System.EventArgs}) in 
System.Windows.Forms.ComboBox.WmReflectCommand (m={msg=0x2111 (WM_REFLECT + WM_COMMAND) hwnd=0x1b211630 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.ComboBox.WndProc (m={msg=0x2111 (WM_REFLECT + WM_COMMAND) hwnd=0x1b211630 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.Control+ControlNativeWindow.OnMessage (m={msg=0x2111 (WM_REFLECT + WM_COMMAND) hwnd=0x1b211630 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.Control+ControlNativeWindow.WndProc (m={msg=0x2111 (WM_REFLECT + WM_COMMAND) hwnd=0x1b211630 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.NativeWindow.DebuggableCallback (hWnd=0x1b211630, msg=8465, wparam=0x11630, lparam=0x1b211630) in 
[Managed to Native Transition] in 
System.Windows.Forms.Control.SendMessage (msg=8465, wparam=0x11630, lparam=0x1b211630) in 
System.Windows.Forms.Control.ReflectMessageInternal (hWnd=0x1b211630, m={msg=0x111 (WM_COMMAND) hwnd=0xf0126 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.Control.WmCommand (m={msg=0x111 (WM_COMMAND) hwnd=0xf0126 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.Control.WndProc (m={msg=0x111 (WM_COMMAND) hwnd=0xf0126 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.ScrollableControl.WndProc (m={msg=0x111 (WM_COMMAND) hwnd=0xf0126 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.Control+ControlNativeWindow.OnMessage (m={msg=0x111 (WM_COMMAND) hwnd=0xf0126 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.Control+ControlNativeWindow.WndProc (m={msg=0x111 (WM_COMMAND) hwnd=0xf0126 wparam=0x11630 lparam=0x1b211630 result=0x0}) in 
System.Windows.Forms.NativeWindow.DebuggableCallback (hWnd=0xf0126, msg=273, wparam=0x11630, lparam=0x1b211630) in 
[Managed to Native Transition] in 
System.Windows.Forms.NativeWindow.DefWndProc (m={msg=0x111 (WM_COMMAND) hwnd=0x1b211630 wparam=0x103e8 lparam=0x7ae0d02 result=0x0}) in 
System.Windows.Forms.Control.DefWndProc (m={msg=0x111 (WM_COMMAND) hwnd=0x1b211630 wparam=0x103e8 lparam=0x7ae0d02 result=0x0}) in 
System.Windows.Forms.Control.WmCommand (m={msg=0x111 (WM_COMMAND) hwnd=0x1b211630 wparam=0x103e8 lparam=0x7ae0d02 result=0x0}) in 
System.Windows.Forms.Control.WndProc (m={msg=0x111 (WM_COMMAND) hwnd=0x1b211630 wparam=0x103e8 lparam=0x7ae0d02 result=0x0}) in 
System.Windows.Forms.ComboBox.WndProc (m={msg=0x111 (WM_COMMAND) hwnd=0x1b211630 wparam=0x103e8 lparam=0x7ae0d02 result=0x0}) in 
System.Windows.Forms.Control+ControlNativeWindow.OnMessage (m={msg=0x111 (WM_COMMAND) hwnd=0x1b211630 wparam=0x103e8 lparam=0x7ae0d02 result=0x0}) in 
System.Windows.Forms.Control+ControlNativeWindow.WndProc (m={msg=0x111 (WM_COMMAND) hwnd=0x1b211630 wparam=0x103e8 lparam=0x7ae0d02 result=0x0}) in 
System.Windows.Forms.NativeWindow.DebuggableCallback (hWnd=0x1b211630, msg=273, wparam=0x103e8, lparam=0x7ae0d02) in 
[Managed to Native Transition] in 
System.Windows.Forms.Application+ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop (dwComponentID=0x1, reason=4, pvLoopData=0) in 
System.Windows.Forms.Application+ThreadContext.RunMessageLoopInner (reason=4, context={System.Windows.Forms.Application.ModalApplicationContext}) in 
System.Windows.Forms.Application+ThreadContext.RunMessageLoop (reason=4, context={System.Windows.Forms.Application.ModalApplicationContext}) in 
System.Windows.Forms.Application.RunDialog (form=Value does not fall within the expected range.) in 
System.Windows.Forms.Form.ShowDialog (owner=(null)) in 
System.Windows.Forms.Form.ShowDialog () in 
Timer.MainForm.ActOnTask (t={xxxx}) in xxxxxxxxxxx\MainForm.cs:6606
Timer.MainForm.EnumFolderTasks () in xxxxxxxx\MainForm.cs:6573
Timer.MainForm.Button1Click (sender={System.Windows.Forms.Button, Text: button1}, e={System.Windows.Forms.MouseEventArgs}) in xxxxxxxxxxxx\MainForm.cs:6615
System.Windows.Forms.Control.OnClick (e={System.Windows.Forms.MouseEventArgs}) in 
System.Windows.Forms.Button.OnClick (e={System.Windows.Forms.MouseEventArgs}) in 
System.Windows.Forms.Button.OnMouseUp (mevent={System.Windows.Forms.MouseEventArgs}) in 
System.Windows.Forms.Control.WmMouseUp (m={msg=0x202 (WM_LBUTTONUP) hwnd=0x22a067a wparam=0x0 lparam=0xa0029 result=0x0}, button=System.Windows.Forms.MouseButtons.Left, clicks=1) in 
System.Windows.Forms.Control.WndProc (m={msg=0x202 (WM_LBUTTONUP) hwnd=0x22a067a wparam=0x0 lparam=0xa0029 result=0x0}) in 
System.Windows.Forms.ButtonBase.WndProc (m={msg=0x202 (WM_LBUTTONUP) hwnd=0x22a067a wparam=0x0 lparam=0xa0029 result=0x0}) in 
System.Windows.Forms.Button.WndProc (m={msg=0x202 (WM_LBUTTONUP) hwnd=0x22a067a wparam=0x0 lparam=0xa0029 result=0x0}) in 
System.Windows.Forms.Control+ControlNativeWindow.OnMessage (m={msg=0x202 (WM_LBUTTONUP) hwnd=0x22a067a wparam=0x0 lparam=0xa0029 result=0x0}) in 
System.Windows.Forms.Control+ControlNativeWindow.WndProc (m={msg=0x202 (WM_LBUTTONUP) hwnd=0x22a067a wparam=0x0 lparam=0xa0029 result=0x0}) in 
System.Windows.Forms.NativeWindow.DebuggableCallback (hWnd=0x22a067a, msg=514, wparam=0x0, lparam=0xa0029) in 
[Managed to Native Transition] in 
System.Windows.Forms.Application+ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop (dwComponentID=0x1, reason=-1, pvLoopData=0) in 
System.Windows.Forms.Application+ThreadContext.RunMessageLoopInner (reason=-1, context={System.Windows.Forms.ApplicationContext}) in 
System.Windows.Forms.Application+ThreadContext.RunMessageLoop (reason=-1, context={System.Windows.Forms.ApplicationContext}) in 
System.Windows.Forms.Application.Run (mainForm=Value does not fall within the expected range.) in 
Timer.Program.Main (args={string[0]}) in xxxxxxx\Program.cs:27