There is something rotten in unofficial builds 851-858 (CopyRates command kills the terminal application). If you got bad luck and already updated to 851, please download this zipped archive terminal.exe build 845 (latest working) and replace the 851 or above terminal.exe (you have to override the browser security).

As you need to prevent updates, find the alias used for launching the MT4, open properties (alt+Enter), and append the /skipupdate trail following the target program:

skipupdate

 

Do not forget to remove this option after reliable update appears.