.net - Existing Silverlight project can't get compiled in the Windows 7

Question

I have Silverlight 4 RIA Project targeting .net 4 framework. the project get compiled on Windows XP no problem. Once we try to compile it under Windows 7 it starts complaining about issues related to the RIA Service. For example, client generated code for the following class will miss the MyArray property.

class Custom
{
   public int A {get;set;}

   public UnitItem[] MyArray {get;set;}
}

where UnitItem defined as

public partial class UnitItem
{
    public int? Id { get; set; }
    public string DisplayValue { get; set; }
    public DateTime? TerminationDate { get; set; }
    public UnitItem[] Subitems { get; set; }
}

has someone came across this issue before? Thanks