Using Internet Explorer (IE) to download the Excel files results in incorrect formatting of the spreadsheets that cannot be fixed by the user. The problem is the result of IE opening the Excel workbook inside the browser window, instead of spawning a new copy of Excel outside IE.
It's easy to get around this problem if you insist on using EI. Just download the Excel file to your computer's Desktop before opening it. To to this
1) Right click on the link to the file you want to open.
2) From the short-cut menu that appears choose "Save Target As..."
3) Use the dialog box that appear to save the file to your desktop (or some other place).
4) After the file is saved, open Excel and open the file by using the File/Open menu.