I need to see the space characters but I can't set it for the life of me.

I went to customize the Whitespace Display Mapping and this is what I found. Notice that the mapping for the space is set to be ".". It doens't work of course:

INS DEL Character Mapping:
            Char Kind: Value Menu Space
            Char:  
            Vector List:
            INS DEL :
                        Vector Characters:
                        INS DEL Char: .
                        INS
            INS
...

I even included this into .emacs

(setq whitespace-display-mappings '((space-mark 32 [46])
       (newline-mark 10 [36 10]) (tab-mark 9 [187
      9] [92 9])))

Still nothing.

Maybe someone know what is the problem here? I just want the whitespace overlay to show the " " character as a ".".

Thanks for your time and help in advance.