Ok, but now I'm starting to think your problem could be due to a network configuration problem. Often times a misconfigured router can give you problems like you're experiencing.
There's two ways to cascade routers via ethernet.
1. LAN-to-LAN
I already gave you instructions on how to configure LAN-to-LAN
http://www.tp-link.com/en/faq-417.html
2. LAN-to-WAN
If you currently have them connected LAN-to-WAN, then the TP-link must be on a different LAN segment so you don't double NAT on the same LAN segment.
Example of correct LAN-to-WAN cascade:
ISP router: Local LAN IP address 192.168.1.1 DHCP server enabled (ethernet connected to ISP router's LAN port)
TP-Link router: Local LAN IP address 192.168.0.1 DHCP server enabled (ethernet connect to TP-link's WAN port)
If you continue to have problems, try changing the TP-Link's local LAN IP address to 192.168.5.1 if you have them cascaded as LAN-to-WAN.
Good luck.