Fixed – the domain mapping works fine when I set it from within the site itself. So simple…
I appreciate the input, it got me thinking in the right direction.
Also: when I use the URL: second.com, it (now) resolves to domain.com, where I have the domain.com WP site (there was some dns latency before this started to work).
When I use the URL second.domain.com, I get the WP page for what I want to get with ‘second.com…’
I used: WordPress MU Domain Mapping, thanks for asking. I read the suggested page by otto as well…
I should say that the page resolves correctly, to a WP home page when I use the URL: second.domain.com. I just need it to work with the URL: second.com.