What I'm curious about is that you said your cisco PIX was handling DNS. Did you setup the AD DNS entries in the PIX DNS properly? You do not have to use windows DNS for AD to work.

Windows doesn't really care who the DNS provider is, just as long as it is setup properly. We use QIP DNS servers instead of the MS DNS on a domain with over 60k clients. It just sounds like you didn't have your domain specified properly on the pix DNS server and it had to use a broadcast or WINS to find the DC.


edit-- nevermind.. reread that post and it was DHCP that you said was on the Pix.. dooh! The situation is still the same though, your ISP DNS didn't have the right information about your AD.