Linksys Wired Router :: E2500 - Cannot Remotely Access Zoneminder On Port 80

I have a Cisco Linksys E2500 modem and I cannot access Zoneminder which is essentially a Linux Security video DVR software package.  It is running on a Ubuntu Linux server. 
 
I have HTTP port 80 forwarded to the the static IP address of the Ubuntu server but I repeatedly get a error indicating that the connection timed out whenever I try to access Zoneminder remotely as in remotely accessing it from a coffee shop.
 
I have absolutely no problem accessing Zoneminder when I on my home local LAN.
 
I can access other software from remote locations on port 4369 with a TCP preferred protocol setting.  That is, port 4369 is forwarded to another Windows workstation with an assigned static IP address. Absolutely no problems with port forwarding of 4369.
 
Also,  I've tested port 80 on the YouGetSignal website which is used for testing port forwarding.  The website indicates that port 80 is closed.  But when I test port 4369, the website reports that the port is open.  Zoneminder which uses port 80 is fully operational when I test port 80 via YouGetsignal.
 
My ISP has told me that they do not block any ports including port 80.