As long as all the columns before Download Link is checked, everything works. 

If I uncheck a columns before the Download Link, it generates an error. Moving up the Download Link works.

[ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: index]
   System.Web.UI.ControlCollection.get_Item(Int32 index) +2057566
   DotNetNuke.Modules.Documents.Document.grdDocuments_ItemCreated(Object sender, DataGridItemEventArgs e) +916

[ModuleLoadException: Feil: Produktark er for øyeblikket ikke tilgjengelig.]
   DotNetNuke.Services.Exceptions.Exceptions.ProcessModuleLoadException(String FriendlyMessage, PortalModuleBase ctrlModule, Exception exc, Boolean DisplayErrorMessage) +481
   DotNetNuke.Services.Exceptions.Exceptions.ProcessModuleLoadException(PortalModuleBase ctrlModule, Exception exc) +100
   DotNetNuke.Modules.Documents.Document.grdDocuments_ItemCreated(Object sender, DataGridItemEventArgs e) +1491
   System.Web.UI.WebControls.DataGrid.OnItemCreated(DataGridItemEventArgs e) +105
   System.Web.UI.WebControls.DataGrid.CreateItem(Int32 itemIndex, Int32 dataSourceIndex, ListItemType itemType, Boolean dataBind, Object dataItem, DataGridColumn[] columns, TableRowCollection rows, PagedDataSource pagedDataSource) +111
   System.Web.UI.WebControls.DataGrid.CreateControlHierarchy(Boolean useDataSource) +1519
   System.Web.UI.WebControls.BaseDataList.OnDataBinding(EventArgs e) +56
   System.Web.UI.WebControls.BaseDataList.DataBind() +72
   DotNetNuke.Modules.Documents.Document.Page_Load(Object sender, EventArgs e) +1787

[ModuleLoadException: Feil: Produktark er for øyeblikket ikke tilgjengelig.]
   DotNetNuke.Services.Exceptions.Exceptions.ProcessModuleLoadException(String FriendlyMessage, PortalModuleBase ctrlModule, Exception exc, Boolean DisplayErrorMessage) +481
   DotNetNuke.Services.Exceptions.Exceptions.ProcessModuleLoadException(PortalModuleBase ctrlModule, Exception exc) +100
   DotNetNuke.Modules.Documents.Document.Page_Load(Object sender, EventArgs e) +1821
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +47
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Control.LoadRecursive() +131
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1061

[PageLoadException: Feil: Produktark er for øyeblikket ikke tilgjengelig.]
   DotNetNuke.Services.Exceptions.Exceptions.ProcessPageLoadException(Exception exc, String URL) +351
   DotNetNuke.Framework.PageBase.Page_Error(Object Source, EventArgs e) +377
   System.Web.UI.TemplateControl.OnError(EventArgs e) +105
   System.Web.UI.Page.HandleError(Exception e) +73
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +6944
   System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +154
   System.Web.UI.Page.ProcessRequest() +86
   System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) +18
   System.Web.UI.Page.ProcessRequest(HttpContext context) +49
   ASP.default_aspx.ProcessRequest(HttpContext context) +29
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +154
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64