I experienced the following message while trying to write to an Excel file from C# code using Interop:

System.Runtime.InteropServices.COMException: Exception from HRESULT: 0x800A03EC
   at System.RuntimeType.ForwardCallToInvokeMember(String memberName, BindingFlags flags, Object target, Int32[] aWrapperTypes, MessageData& msgData)
   at Microsoft.Office.Interop.Excel.Range.set__Default(Object RowIndex, Object ColumnIndex, Object )

The problem was down to inserting values at a zero index.  Excel documents begin their range at 1, not 0.  Now that’s a mindshift for a long-time zero-based programmer!