Antonio,
I came into this question a little late so I'm not sure how it was back when you asked it, but right now the problem I see is that the page that does exist ( http://www.comparativadebancos.com/mejores-depositos-bancarios-de-marzo-de-2011/ ) has a rel canonical tag pointing to the page that doesn't exist ( http://www.comparativadebancos.com/depositos/marzo/ ), which returns a 404 response code.
I think right now the best thing you can do would be to change the rel canonical tag on /mejores-depositos-bancarios-de-marzo-de-2011/ to be http://www.comparativadebancos.com/mejores-depositos-bancarios-de-marzo-de-2011/ .
