We have a Sharepoint site which uses search.

We get the following error:

```

Unable to validate data.   at 
System.Web.Configuration.MachineKeySection.EncryptOrDecryptData
(Boolean fEncrypt, Byte[] buf, Byte[] modifier, Int32 start, Int32 length, 
IVType ivType, Boolean useValidationSymAlgo) 
   at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)

```

After a bit of testing we have found that the error occurs when we use DateKeyNames on a GridView control.

Not sure why there should be any combination between Search, this error and DataKeyNames.

Any ideas?

Update: Here is some code

```
[Guid("8891224e-e830-4ffa-afbd-f789583d8d14")]
    public class TestErrorGridView : System.Web.UI.WebControls.WebParts.WebPart
    {
        Control ascxToAdd;
        public TestErrorGridView()
        {
        }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);

        }

        protected override void CreateChildControls()
        {

            base.CreateChildControls();
            Table test = new Table();
            TestBindObject t1 = new TestBindObject() { ID = 1, Name = "Test" };
            List<TestBindObject> l1 = new List<TestBindObject>();
            l1.Add(t1);
            SPGridView testGrid = new SPGridView() { AutoGenerateColumns = false};
            BoundField header = new BoundField();
            header.DataField = "ID";
            BoundField name = new BoundField();
            name.DataField = "Name";
            testGrid.Columns.Add(header);
            testGrid.Columns.Add(name);
            testGrid.DataSource = l1;
            testGrid.DataBind();
            // If you comment out this line search works
            testGrid.DataKeyNames = new string[] { "ID" };
            this.Controls.Add(testGrid);

            base.CreateChildControls();
            SPGridView testGrid = new SPGridView() { AutoGenerateColumns = false, EnableViewState=false };

            testGrid.DataKeyNames = new string[] { "testid" };  

            this.Controls.Add(testGrid);

        }
    }

public class TestBindObject
{
   public int ID { get; set; }
   public string Name { get; set; }
}

```

**UPDATE**

This error occurrs on the developer machines, so it is not realated to machine keys being different on different machines in a cluster.

One of the developers has MOSS installed, he does not get the error. The developers who have just WSS installed get the error.

**UPDATE 2**

Have added datasource to code