This error is quite explanatory in JSF.
I got once in a while when I work with dynamic generation of the components.
If you have this, the most common cause of this error would be you are trying to attach the an html component from your bean again.
Especially, if you have session scoped managed bean and you are attaching dynamically elements, may be one of your methods has already attached the component to the view (like the grid you are using for your component) and the other method is trying to attach it again.
If that is the case you might need to check the existence of the component in the grid (or any component you are using) before attaching it.
Also: see how to add session bean to request