Hi,
I think your excel file is corrupt. You can try a popular Excel file recovery tool called Advanced Excel Repair to repair your Excel file. It is a powerful tool to repair corrupt or damaged Excel files.
Detailed information about Advanced Excel Repair can be found at
Advanced Excel Repair - Repair corrupt Excel files. Fix Excel files.
And you can also download a free demo version at
http://www.datanumen.com/aer/aer.exe
Alan