[bitmedley]

I checked and New Zealand actually uses a comma as the separator, not a semi-colon. You can verify this by going to Control Panel -> Region -> Change to: English (New Zealand) -> Additional settings... -> List separator

A semi-colon is generally used as the default list separator when the region/locale uses a comma as the decimal separator for numbers. For example Dutch (Netherlands) uses a comma for the decimal separator (ex. 3,14) whereas in English (US) we use a decimal point (ex 3.14). If comma were used as the default list separator in such a region then all floating point numbers would need to be quoted (ex. "3,14") which would make the size of the CSV file larger and also make the file less human-readable

[billforsternz]

Interesting. Certainly it was only a subset of customers who were complaining, and in the office it was a subset of Excel installations which could reproduce the problem. There's no doubt what the problem was and how to fix it. There is a doubt about exactly which Excel and Windows combinations are problematic, and how prevalent that combination is amongst New Zealand installations.