You could try to insert the HTML tag for line break - <br> - like this:
This is the first line<br>and this is the second line
I have no idea if this will work, but it's worth a try.
May be it works, and may be the browser will display the <br> as text.
That does work but then I have <br> tags in the caption which make no sense if you are looking at the iptc fields.
One website admin said its to do with character sets and they use Latin-1 but no idea on that.