I did finally get it resolved but to be honest, I both can't remember exactly what I did a couple of years ago [think it had to do Enable Promotion of Distributed Transaction for RPC] and it's one of those things that I wish I had left broken. One of our developers ran wild with it and put it in pretty much everything he did. Querying the AD for us is about 2000 times slower than querying the SQL server, doing it thousands of times a day makes for some long days.