also worth checking your http server isn't setup to bind to a specific legacy ip address (from an old setup).

if you are using apache - check httpd.conf .. will be the 'Listen lines'

if you are windows again check bind addresses in IIS, also make sure the firewall hasn't detected the new network and set you up a nice new restrictive profile.

you could use wireshark installed on the server to check for traffic reaching it; if you can't install it on the server, mirror the network port and use it on a laptop.

just to check the 2860n is connected directly to your telephone line - there isn't a legacy BT router in the mix?***** just re-looked at your NAT sessions screen print - this doesn't appear to be the case

Can you access your web server from the internal network using address 192.168.1.77 ?

Cheers
Adam