form property - Collection

[Carolina Costa]

Hi everyone,
    I have a form (extends ActionForm) that has a List property called "procedimentos":

    private List procedimentos;

       public List getProcedimentos() {
            return this.procedimentos;
        }

        public void setProcedimentos(List proc){            
            this.procedimentos = proc;
        }

This list  is created in my business logic layer, and it is instatiated as a Vector 
and  populated with Bean called Procedimento which has a property codigoTermoTecnico;

I'm using <logic:iterate> tag to run througth this collection and show its values, 
this piece of code shows my jsp:
 <logic:iterate id="x" property="procedimentos" indexId="i">
   <td align="center">
   <bean:write name="x" property="codigoTermoTecnico"/>
  </td>
 </tr>
 </logic:iterate>

when I call this jsp page i have the following error:
org.apache.jasper.JasperException

root cause 

java.lang.NullPointerException
I can't understand that since I'm priting the Form contents in my Action and the List 
is populatedAnyone could help me?! thanks in advance..Carolina