RCDC problem

I have a custom object "Computer" and I have a user attribute "Computers" (a multivalued reference attribute), which can reference to one or more Computer objects. However, when I put the following control to the user creation RCDC page, FIM complains that that there is a problem in the DCDC configuration. Any insights on what I am doing wrong? Thanks a lot in advance !!!

      <my:Control my:Name="Computers my:TypeName="UocIdentityPicker" my:Caption="{Binding Source=schema, Path=Computers.DisplayName}" my:Description="{Binding Source=schema, Path=Computers.Description}">
          <my:Properties>
              <my:Property my:Name="ReadOnly" my:Value="false" />
              <my:Property my:Name="Required" my:Value="{Binding Source=schema, Path=Computers.Required}" />
              <my:Property my:Name="Mode" my:Value="MultipleResult"/>
              <my:Property my:Name="ColumnsToDisplay" my:Value="DisplayName, ObjectType" />
              <my:Property my:Name="AttributesToSearch" my:Value="DisplayName" />
              <my:Property my:Name="Value" my:Value="{Binding Source=object, Path=Computers, Mode=TwoWay}" />
              <my:Property my:Name="ResultObjectType" my:Value="Computer"/>
              <my:Property my:Name="ListViewTitle" my:Value="Select a Computer" />
              <my:Property my:Name="ObjectTypes" my:Value="Computer" />
              <my:Property my:Name="Hint" my:Value="{Binding Source=schema, Path=Computers.Hint}" />
          </my:Properties>
      </my:Control>