This is more of an FYI because I am not sure if you can fix it. However, if an image is placed into the print header, Excel 2010 puts the resulting workbook into a protected state and displays a warning. Here is sample code (directly from the Aspose site) that illustrates the issue:
static void Main(string[] args)
{
Workbook workbook = new Workbook();
string logo_url = @"C:\temp\logo.jpg";
FileStream inFile;
byte[] binaryData;
inFile = new System.IO.FileStream(logo_url, System.IO.FileMode.Open, System.IO.FileAccess.Read);
binaryData = new Byte[inFile.Length];
long bytesRead = inFile.Read(binaryData, 0, (int)inFile.Length);
PageSetup pageSetup = workbook.Worksheets[0].PageSetup;
pageSetup.SetHeaderPicture(1, binaryData);
pageSetup.SetHeader(1, "&G");
pageSetup.SetHeader(2, "&A");
workbook.Save(@"C:\temp\Class3.xls");
inFile.Close();
}