Please make sure you have closed down the launcher before trying to replace the file and then restart it once you have replaced the file.
Download instructions for each Browser type :-
Internet Explorer : Right click on the link and choose "Save Target As", you will then need to type in the file name (just the file name and not the path part, eg for Win32\data.ovx you would just type data.ovx)
Chrome & Firefox : Right click on the link and choose "Save Link As", you will then need to type in the file name (just the file name and not the path part, eg for Win32\data.ovx you would just type data.ovx)