There seems to be a bug in the importtable where sometimes instead of a CSV (comma separated values), it imports a WSV (whatever-separator-you-have-in-Windows separated values). Actually, this is the same bug that Excel seems to have had for ages.
I created a CSV on my computer with international settings (using a comma between fields and a dot as decimal separator) and sent it to a customer with Dutch settings (using a semicolon between fields and a comma as decimal separator). So the importtable() command failed.
How can I make importtable() import actual comma separated values without creating a separate CSV source for each possible locale?