Keyboard hook freeze

    public class Program
    {
        /*
         * Hook Variables
         */
        private const int WH_KEYBOARD_LL = 13;
        private const int WM_KEYDOWN = 0x0100;
        private const int VK_F1 = 0x70;
        private static LowLevelKeyboardProc _proc = HookCallback;
        private static IntPtr _hookID = IntPtr.Zero;

        /*
         * Hook DllImports
         */
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetModuleHandle(string lpModuleName);

        /*
         * Variables
         */
        public delegate void TheKeyEventHandler();
        public static event TheKeyEventHandler OnKey;
        private static Program instance = new Program();
        public static Program Instance
        {
            get
            {
                return instance;
            }
        }

        /*
         * Main
         */
        [STAThread]
        static void Main()
        {

        }

        /*
         * Constructor
         */
        private Program()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            _hookID = SetHook(_proc);
            Form = new Form1();
            OnKey += Program_OnKeyPress;
            Application.Run(Form);
            UnhookWindowsHookEx(_hookID);
        }

        void Program_OnKeyPress()
        {
            // Interact with the form.
        }

        /*
         * Hook Methods
         */
        private static IntPtr SetHook(LowLevelKeyboardProc proc)
        {
            using (Process curProcess = Process.GetCurrentProcess())
            using (ProcessModule curModule = curProcess.MainModule)
            {
                return SetWindowsHookEx(WH_KEYBOARD_LL, proc, GetModuleHandle(curModule.ModuleName), 0);
            }
        }

        private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

        private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
        {
            if (nCode >= 0)
            {
                Keys number = (Keys)Marshal.ReadInt32(lParam);
                OnKey();
            }
            return CallNextHookEx(IntPtr.Zero, nCode, wParam, lParam);
        }
    }