Even i am facing the similar issue. i need to freeze the header pane of an excel exported from ultrawebgrid.here is my code

Infragistics.Excel.Workbook StandardModule = new Infragistics.Excel.Workbook();

StandardModule.Worksheets.Add("Module");

StandardModule.Worksheets["StandardModule"].DisplayOptions.PanesAreFrozen = true;
StandardModule.Worksheets["StandardModule"].DisplayOptions.FrozenPaneSettings.FrozenRows = 1;

this.uwgSearchGridExporter.Export(this.uwgExportToExcel, StandardModule.Worksheets["Module"]);

when i open the excel, i am getting "File error : data may have been lost", bt the file opens and the header pane is frozen.
i am having Excel 2007 in my machine.