192.168.2.100 is online but isn't responding to connections on port 4444

I'm a newbie and I'm having a problem accessing the WebAdmin page. My hardware setup is as follows:

[modem]<->[Astaro]<->[router/DHCP/NAT]<->[switch]<->[pc's]

For various reasons, I want my Netgear FVS338 firewall/router to be the DHCP/NAT server for my LAN instead of the Astaro. I just want the Astaro v8 Home Edition to be an internet security device. The eth0 port on the Astaro is connected to the WAN port of the FVS338.

When I connnect a pc directly to the Astaro (a spare pc) I can access the WebAdmin page with no problem. The Astaro is connected to the internet because I've already received several email notifications from it.

However, when I try to access the WebAdmin page using the above mentioned hardware setup I get the following error message from Windows 7 Network Diagnostics:

"resource (192.168.2.100) is online but isn't responding to connection attempts. The remote computer isn't responding to connections on port 4444, possibly due to firewall or security settings or because it might be temporarily unavailable. Windows couldn't find any problems with the firewall on your computer."

I can successfully ping 192.168.2.100.

I'm using Norton Internet Security 2012 but I don't think that it's causing a problem because I can access the WebAdmin page when the pc is connected directly to the Astaro.

Any suggestions?