I’ve just finished wrestling with a problem one of our academics was having with a spreadsheet.

Excel has detected that (file name).csv is a SLYK file, but cannot load it.  Either the file has errors or is not a SLYK file format.  Click to try to open the file in a different format.

sylk

I eventually found this on the Microsoft site

When you try to open a text file or a comma-separated variable (CSV) file, you may receive the following error message:
SYLK: File format is not valid

This problem occurs when you open a text file or CSV file and the first two characters of the file are the uppercase letters “I” and “D”. For example, the text file may contain the following text:
ID,    STATUS
123,  open
456,  closed

Note This problem does not occur if the first two letters are lowercase “i” and “d”.

You can’t use ID in cell 1A!!   It’s a spreadsheet, you’d think even an echidna would realise there’s a pretty fair chance of ID appearing in the first cell.

That’s not an error that’s a bug.