Error to deserialize The InnerException message was 'ValueType 'System.Int32' cannot be null
<p>I am getting this error sporadically (it happened all the time about 2 hours ago, but now I am not getting the error) when bring up K2 forms (that uses K2 SmartObjects that calls WCF Service).
When I kept getting the error, it seems to be at different functions</p>

<p><a href="http://tempuri.org/:GetAccountDetailsForWorkflowResult" rel="nofollow noreferrer">http://tempuri.org/:GetAccountDetailsForWorkflowResult</a>
   <a href="http://tempuri.org/:GetNewAccountFormInitializationDataResult" rel="nofollow noreferrer">http://tempuri.org/:GetNewAccountFormInitializationDataResult</a></p>

<p>The InnerException message was always the same: 'ValueType 'System.Int32' cannot be null.'</p>

<pre><code>Error: The formatter threw an exception while trying to deserialize the    message: There was an error while trying to deserialize parameter http://tempuri.org/:GetAccountDetailsForWorkflowResult. The InnerException message was 'ValueType 'System.Int32' cannot be null.'. Please see InnerException for more details.
</code></pre>

<p>Why did I get this error, and why now when I bring up the same workflows, I am not getting the error anymore ?
Also, we tested the same workflows and service on 2 testing environments, and it works with no error.</p>

<p>Could it be a problem with the network or the server ?</p>

<p>How do I find what variables gives the error The InnerException message was 'ValueType 'System.Int32' cannot be null.' ?</p>

<p>This is the class</p>

<pre><code>  namespace Nuveen.Core.Entities
{
    public class SPONSOR
    {
        [Key]
        [Column(Order = 0)]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int intRelationshipID { get; set; }

        [Key]
        [Column(Order = 1)]
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int intSponsorID { get; set; }
        public virtual SPONSOR Sponsor { get; set; }

        [Key]
        [Column(Order = 2)]
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int intFirmID { get; set; }
        public virtual FIRM Firm { get; set; }
</code></pre>

<p><code>public int? numFO { get; set; }</code>  --> I just added this column (to be added to the database)</p>

<pre><code>[StringLength(250)]
public string vchSalesTeam { get; set; } --&gt; I just added this column also
</code></pre>