Can’t open excel spreadsheet in IE6

I can’t open an Excel 2000 document in IE6. An Excel window opens within the browser, but the spreadsheet isn’t displayed. My coworker can open it. The document contains several worksheets and one contains a textbox (which might be a problem). I need to be able to view, from this website, 22 worksheets per catagory with 4 catagories total. Microsoft doesn’t address this as all! Help!!!