i tried to search, but I didn't find anything. So, I have to domains:
On domain1.com, I have a WP MU install, with domain mapping enabled.
I created a blog, and I mapped the domain2.net to this blog - everything is correct.
I created a second blog, and I mapped subdomain.domain2.net to this blog - it isn't working.
I think, this should be a server issue. I'm testing on the wpwebhost.com.