Multi Network / Multi Site Login problem

We encountered a strange problem in our WP. I’ll try to describe our Setup first.
OS: Solaris 10
Webserver: Apache 2.2.16
WP: 3.2.1

Overview of our WP Networks:
http://i.imgur.com/vG57n.png

We use
Wordpress MU Domain Mapping
WP Multi-Network
LDAP Authentication Plug-in

All our users authenticate against our central LDAP server. All our users can create a blog on our WP Network 1. This was the first available wordpress instance.
We created three WP networks with the WP multi-network plugin and mapped domains to each of it.
Now we encountered a problem in the case:
– The user has never logged in to any of the wp networks
– We add the user manually as Administrator (not network admin) in the WP Network 2
– After login to WP Network 2, everything works as expected.
But if the user now tries to create a personal blog in the WP-Network 1, WP is displays a error message:
“You attempted to access the “Domain 1 Network” dashboard, but you do not currently have privileges on this site. If you believe you should be able to access the “Domain 1 Network” dashboard, please contact your network administrator.”

In the case the user first logs in to WP Network 1, and then gets added in WP Network 2 as an Administrator, everything works fine.

I really dont know if the error is related to the LDAP Plugin, the WP Multi-Network Plugin, WP itself or our multi Network setup (is there a best-practice document?)