Router cascade configuration problem

Hi all,

I have a very strange problem with my router configuration.

I currently live in France and use Orange as internet (+TV and phone) provider: this means that I have to use their "LiveBox" (Router+Modem) to connect to the internet.
The LiveBox doesn't support wifi QoS and is generally quite awful, so I decided to plug-in a second router to be used as wireless hub to connect to. It is the TP-Link TL-WDR4300.

I have done this before and so I applied the standard configuration: connect two ethernet ports of the two routers, disable DHCP on the second one. Now, when I try to connect to the wireless network my MacBook and my Galaxy Nexus connect and work without problems, while my windows desktop PC says that the network doesn't have internet access.
Some other times it works for it too, but only for short times.
It though it could be because of wireless interference, but changing channel didn't solve the issue.

Now the PC can only connect to the 2.4Ghz wireless network (the router is dual band) but even forcing the other devices to connect to the same network doesn't reproduce the problem.

I am running Windows 7 64bit, with a standard network configuration.
Please note that if I plug-in a different router instead of the TP-Link, everything works well.

Can anybody guess what the problem is?

Mad Baron

Would be a good question to get some answers on. I tried going the router as access point route a couple weeks ago and as soon as I got it all set up, I could never gain access to that router's web interface, despite following a tutorial to the letter.