Ah, CSV and Excel
I remember a conversation with a "data analyst" at a major insurance company, who was meant to send me a .csv but sent an .xls instead. Easy mistake to make, sent an email to remind him and got a .csv by return. All good so far, but the file wouldn't load. When I opened it in Notepad++ to check the format, it became obvious that what the "analyst" had done was to rename the original spreadsheet file... Because they were a customer I had to limit my sarcasm in my next message.