Below is the code.
I also created a custom validator to check the value, and the value is null. It is strange because when I see the rendered page I get to see the listbox correctly. Thanks in advance.

public SelectItem[] getTypesItems() {
List list = ClientManager.getList();
Iterator i = list.iterator();
List toItem = new ArrayList();
List toItemDesc = new ArrayList();

Client next = null;
while (i.hasNext()) {
next = (Client) i.next();
toItem.add(next.getId().toString());
toItemDesc.add(next.getId().toString());
}
return JSFUtils.list2SelectItem(toItem, toItemDesc);
}

======
JSFUtils.list2SelectItem goes like this:

public static SelectItem [] list2SelectItem(List list, List label) {
SelectItem [] toReturn=new SelectItem[list.size()];
int count=0;
try {
Iterator i=list.iterator();
Iterator i2=label.iterator();
String str1="";
String str2="";
while(i.hasNext()||i2.hasNext()) {
str1=i.next().toString();
str2=i2.next().toString();
System.out.println("str1:<"+str1+"> str2:<"+str2+">");
toReturn[count]=new SelectItem(str1,str2);
count++;
}
} catch(Exception e) {
toReturn=null;
e.printStackTrace();
}

return toReturn;
}
=====

It is a Long. :)

Hi, thank you for your answers. You were right, my error was a convertion problem. It was not richfaces who caused it, it was myfaces. My code used to work because myfaces wasn't sticking to the JSF specification, but aftwr version 1.1.5 they fixed the error, and throwed it to me.
If is it useful for someone read the link in myfaces wiki:
http://wiki.apache.org/myfaces/FAQ at the end of the page.

Greetings to all, and thank you,

Luis