Files are not accepted during the upload process: 


You receive one of the following red error messages: 


The CSV appears to be corrupt near record '15' field '29 at position '2063'. (Or something similar)
This is usually caused by using a csv file with dates formed dd/mm/yyyy.  To correct this form your dates yyyy-mm-dd or save the csv as an xls which will automatically handle the date formatting for you.


Object reference not set to an instance of an object.
Make sure have included column headings in your data file for each column that contains data.

and

Make sure you only try and upload data in one worksheet per xls file.

and

Make sure worksheets names only have alphanumeric characters in their names and no spaces

and

Make the sure file names of your upload files only contain one '.' ie myfilename.xls and not my.file.name.xls