Had the same issue with version 6.1.3.108.  I think it has something to do with targeting framework 4.0.  

Here is the markup for the controls in question.

the code expects everything before the DataGrid to be added to the controls collection as a single literal control.  Instead each tag is added as a literal or databoundliteral control pushing the DataGrid from [1] to [5].

So DataGrid extensionsGrid = item.Controls[1] as DataGrid; references the h2 tag and not the grid.  As a result a null reference is passed into the BindGrid method.

Don't know why the dev team is using an explicit control index instead of using item.FindControl("extensionsGrid") but , that's what I did to correct the error.

Yes. Exactly. I done!