I have an error, but not always it reproduces.

This is a aspx page that shows some information loaded in Page_Load() function.

In most of navigators works fine, but in some computers and some navigators (none in particular) it doesn't works.

Can anyone help me?

Thanks in advance

[NullReferenceException: Object reference not set to an instance of an object.]
   ASP.cmstemplates_cocktailsite_sales_paso1_aspx.__RenderContent1(HtmlTextWriter __w, Control parameterContainer) +1665
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +130
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +149
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +245
   System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +393
   System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +48
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +110
   ASP.cmstemplates_cocktailsite_sales_masterpagesales_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) +313
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +130
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +149
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +245
   System.Web.UI.Page.Render(HtmlTextWriter writer) +39
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +149
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5362