That is a real biggie! Not only I was able to solve the problem, I was able to do that quite cleanly and elegantly.
The code that uses it doesn't even know that there is all sort of inter AppDomains communications, and I'm also closing the database connection fast, so if you forget NQA open, you're not wasting any precious connections :-)
Now I just need to fix some stuff regarding circular references, and I think that I'm all set to move to Nhiberante 0.9 and release a new version.