Coercion error in grid

[Stephane Decleire]

Hi all,

When i try to show a list of my objects in a grid, i get the following 
error :
"Could not find a coercion from type 
org.hibernate.collection.PersistentSet to type com.mycompany.MyType"

Here is my component code :

public class UserAdsList {

   @Parameter(required = true)
   private List<Ad> ads = null;
   public List<Ad> getAds() {
       return ads;
   }
   public void setAds(List<Ad> ads) {
       this.ads = ads;
   }
}


and template :

<t:container xmlns:t="http://tapestry.apache.org/schema/tapestry_5_0_0.xsd";>

<t:grid source="ads"/>

</t:container>

Any idea ?

Stephane