ENDIAN Firewall - Active Directory + Domain Connection Loss

Right, I've been on a research mission for the past few months for work to find a firewall that will allow domain connections through but also allow the proxy to be forwarded through to an internet filtering system (Bloxx)

I've tried several different firewall programs from IP-Cop, Smoothwall, M0n0wall, pfSense and now I'm trying Endian 2.2.... I keep running into a huge problem.

The Firewall is set up with a Red + Green configuration. Green being the isolated network which we want to use for any laptop, some will be on a domain and the rest will be not and Red being the main network with the Domain servers on. How it seems to be working at the moment is when a cl of students switch on the laptops to log into the network, 1 or 2 will be allowed access through the firewall to the domain servers, then the rest start getting either 'Domain is currently unavailable' or profile issues which then log them back out after 30 seconds.... if they retry a few times most are able to log in, however network drives with their home areas on will drop for no reason. I have opened up all the related windows networking and active directory ports which are required but that had no effect.

I don't know if its a multiple connections issue, whether its a firewall issue, traffic issue... but its just not happening.... anyone who could shed any light on this please let me know.

Cheers.