On Dec 5, 2009, at 1:04 AM, Daniel Martins wrote:

> Thank you very much
>
> I did everything you suggested and everything worked nicely
>
>
> But even using load-libray
>
> org-latex
>
> and
>
> org-beamer
>
> I received
>
>
> Loading /home/daniel/emacs-lisp/org-mode/lisp/org-beamer.el  
> (source)...done
> Loading /home/daniel/emacs-lisp/org-mode/lisp/org-latex.el  
> (source)...done
> Select command:
> Exporting to LaTeX...
> or: No definition for class `beamer' in `org-export-latex-classes'

If you have customized org-export-latex-classes before, then the value  
you stored will overwrite the new default (which contains the beamer  
entry.  Two ways to fix this:

1. Remove you customization of this variable, restart Emacs, and  
customize again to redo the changed you have made earlier.  THis is  
the safest way.

OR

2. Customize the variable and create a new entry for beamer, with this:
     ("beamer"
      "\\documentclass{beamer}
\\usepackage[utf8]{inputenc}
\\usepackage[T1]{fontenc}
\\usepackage{graphicx}
\\usepackage{longtable}
\\usepackage{float}
\\usepackage{wrapfig}
\\usepackage{soul}
\\usepackage{amssymb}
\\usepackage{hyperref}"
      org-beamer-sectioning
))


So in your customize buffer it must look like this: