Question : SBS2003 no http access just https

SBS2003 Standard single network card, Bigpond ADSL Modem Router
Server running DHCP

Everything working ok except neither server nor workstations
Can access web sites unless there https
email & remote access all ok

Has been running fine for a few years now & all of a sudden this
The Modem router appears ok with Port 3389 & 443 Open to the server

Have even tried to open port 80 no luck
No direct access to the server just remote for now

Answer : SBS2003 no http access just https

well, yoiur routing fine.  Kinda figured that by https working.  Port 80 is being blocked somewhere.  None of your machines can get to http right?  servers or clients inbound or outbound?  Is there a firewall somewhere?  What are these 172.x.x.x devices?