JCH_

As Davidt2005 mentioned. Its sounds as though it is some form of routing issue if your smoothwall appliance is dropping packets and not returning them (Presumably the firewall configuration is setup correctly). Without stating the obvious potentially (I dont know your setup) you need to ensure that in the Smoothwall > Routing > Subnets all of your static routes are setup correctly including subnet and gateway for each of the internal networks on the other side of your core, but this may be fine already. I would also expect smoothwall to drop all packets if your routing is not setup correctly. They would all drop instead of a select few. It is hard to determine a true cause without having more information on the network setup.