|There are a few possibilities. |
First off, in order to have both cams viewable using the same external IP address, you WILL need to use port forwarding. Be sure that the port numbers are the same for the external and internal addresses.
Now, what could be happening is that either your ISP is blocking traffic on port 8080 or your router is not properly passing port 8080.
Some ISPs block common HTTP ports like 80, 88, 81, 1080, and 8080 to ensure that their home users are not running web servers over "consumer" grade connections. This allows them to charge for "business" based connections to allow those ports.
Also, the external management interface of your router may be set to port 8080, and even if it is not enabled in the firmware, the traffic will get captured by the router's firewall and dropped since the feature is not enabled.
Both of these scenarios can be fixed by changing the non-working camera's port number to a different port, like 8084.
If you do this and are still having issues, then it is possible that it is a wireless issue, although I do not believe that is the case here.
Please let me know if this fixed the problem or if you are still having issues.
IT Desktop & Network Consultant - MOS Master Certified, MCP, MCITP - Windows 7, CCNA Certificate Pending, A+, Network +