Yes, the Infragistics3 Excel is causing the error, but turns out they were trying to import a sheet that had pivot tables and all sorts of other funky formatting. The sheet that I need to use that is just a basic sheet works just fine.

Here is the error just in case you may or may not want to handle it differently.

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A IPackagePart with the same name already belongs to this IPackage.
A IPackage cannot contain parts with identical names. Note that the check for duplicate values is case-insensitive.

at Infragistics.Excel.Serialization.Excel2007.PackageConformanceManager.VerifyPackageConformance(IPackage package)
at Infragistics.Excel.Serialization.Excel2007.Excel2007WorkbookSerializationManager.LoadWorkbookContents()
at Infragistics.Excel.Serialization.WorkbookSerializationManager.Load()
at Infragistics.Excel.Workbook.LoadXLSXFile(Workbook workbook, Stream stream, IPackageFactory packageFactory, Boolean verifyExcel2007Xml) 

For Excel 2007 support in Windows Forms, you should use the Infragistics3.Excel.v8.3 assembly.  The Infragistics35.Excel.v8.3 is used for our ASP.NET CLR 3.5 controls only.

Does using the Infragistics3 Excel assembly prevent this IPackage error?  If not, can you please provide the full exception text and stack trace?

Actually one more thing here.

I had to switch to the Infragistics3.Excel.v8.3.dll to use that exporter.  Trying to import a 2007 xlsx file I get some funky error about duplicate IPackage something or rather.  With the Infragistics35.Excel.v8.3.dll I was able to import that same sheet just fine.

I tried a search here on the IPackage error and got no hits. Any ideas?

Bah..

I knew it had to be something easy. Thanks