Update_attributes does not work

Rails
1

I have problems using the update_attributes function in my controller.
Sometimes works and sometimes doesn’t. I can always make it work if I
put a breakpoint just before the update_attributes function. What does
that mean?. Why is it doing this?.
Please help. If I don’t get this working I’ll quit Rails for good, it’s
caused me a lot of trouble, I’m starting not to like it.
Thanks.

Here is my code:

def update
@persona = Persona.find(params[:id])
@persona.fecha_modificacion = Time.now
@persona.modificacion_user_id = 1

if @persona.fecha_creacion? == nil
  @persona.fecha_creacion = @persona.fecha_modificacion
  @persona.creacion_user_id = @persona.modificacion_user_id
  @persona.eliminado = 0
end

#breakpoint
if @persona.update_attributes(params[:persona])
  flash[:notice] = 'Persona was successfully updated.'
  redirect_to :action => 'ver', :id => @persona
else
  render :action => 'list'
end

end