Open CuteSoft_Client\CuteEditor\SpellCheck.aspx file and modify the following code:

 

// check if a dictionary exists for the culture, if so load it
             string cultureDictionary = String.Concat (culture, ".dic");
    if (File.Exists (folderName +"\\"+ cultureDictionary))
    {   
    this.WordDictionary.DictionaryFile = cultureDictionary;
    }
    else
    {
     this.WordDictionary.DictionaryFile = "en-US.dic";
    }