There might cause a Pinvoke exception happen when start edit a cell, this problem has been fixed after 0.8.5.1. To fix this problem in development environment, try the following steps:

1. Open ReoGrid project
2. Open source file Common/Win32.cs
3. Find definition of 'SendMessage' method like this:
   public static extern int SendMessage(IntPtr hWnd, uint Msg, long wParam, long lParam);
   

4. Change last two parameters from long to IntPtr, as below:
   public static extern int SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);
   

5. Find caller of SendMessage method in ReoGridControl.cs, change arguments to
   new IntPtr(value)
   

6. Rebuild and done.