Problem with validating <h:selectManyListbox>

[phantasmo]

I have an Item entity associated with many Tag entities.
The page for adding new Items has the following snippet:

<s:decorate id="tagsField" template="layout/edit.xhtml">
                <ui:define name="label">Tags</ui:define>
                <h:selectManyListbox style="width: 300px;" size="10" value="#{itemHome.instance.tags}">
                         <f:validator validatorId="TagValidator"/>
                         <s:selectItems var="t" value="#{allTags}" label="#{t.name}" />
                         <s:convertEntity />
                    </h:selectManyListbox>                             
            </s:decorate>

This is TagValidator code:

public void validate(FacesContext ctxt, UIComponent cmp, Object val) {  

          String message = null;  

          try {  
               List selectedVals = (List)val;
               int numberOfTags = 0;
               if (selectedVals != null) {
                    numberOfTags = selectedVals.size();
               }
               if (numberOfTags > 5)
                    message = "No more than 5 tags are allowed!";
          } catch (Exception e){               
               message = "Something went wrong while processing tags!";
          }

          if (message != null) { 
               FacesMessage msg = new FacesMessage(  
                         FacesMessage.SEVERITY_ERROR, message, message);  
               throw new ValidatorException(msg);  
          }  
     }  

Now, when I press Save, although the validation passes, I get the message The value is invalid and the operation fails. I concluded it must have something to do Seam, as my custom validation passes.

Any idea what this may be related to? Any help is appreciated.

[phantasmo]

Solved. Sorry for the inconvenience caused.
The problem was with the *allTags* (used to populate <h:selectManyListbox>) variable scope. It seems I had changed it at some point in time and completely forgot about it.