I entered Nokia's applications (not in meamo.org), then I clicked on Update and it wrote me: "There is no catalog. "
What is this?

I'm no expert BUT: you need to have the application respository added to application manager in order to install the application.. you may want to look here http://repository.maemo.org/ or here http://maemobriefs.blogspot.com/2010...-for-n900.html