You may have uploaded an Excel file (.xls) instead of a CSV (.csv) file. To save an Excel file as CSV you need to follow the steps below:
If a dialog box is displayed, warning that the 'selected file type will only save active sheet', click OK.
Your CSV file may also have spurious characters - if you have created your CSV file in Excel. To remove these follow the instructions below:
Alternatively to overcome such problems you might want to consider using the template provided. This can be accessed from the bulk upload page.