Please send your dired-x.el in sed.nivo [a_t_] gmail [dot] com
In my Emacs 'C-h k M-o' displayes
M-o runs the command dired-omit-toggle
which is an interactive compiled Lisp function in `dired-x'.
(dired-omit-toggle &optional FLAG)
.....
I try '(dired-omit-mode 1)' , but
Symbol's function definition is void: dired-omit-mode
And '(dired-omit-toggle 1)' don't make any effect.