Question: I run ubuntu 10.04 and I installed a wlan like:

[modem]---ethernet cable--[wireless router]----ethernet cable--[my PC]

Computers using the wireless network can access all pages normally.

I, on the other hand, using ethernet, am limited:

1. I cant login on facebook (it enters facebook.com if I'm not logged in, but once
I log in everything stops working)
2. I can't post (but can browse) on stackoverflow and similar
3. I can't post (but can browse) on ubuntuforums.org

When I skip the wireless router and do:

[modem]----ethernet cable--[my PC]

I can access everything normally.

I inspected the wireless router page but everything seems normal to me (but I'm not an 'expert')

Some help please. I can post output of any command here.

**UPDATE 1:**
I found out that I cant upload images too while connected to the router.

DHCP config for modem
![enter image description here](https://i.stack.imgur.com/LJwB0.png)

Router  

![enter image description here](https://i.stack.imgur.com/q6YmX.png)

Answer: 
Most likely, you have router modem plugged into one of your router's LAN ports rather than its WAN/Internet port. The best solution is probably to switch your modem to bridging mode and connect it to your router's Internet/WAN port.

Alternately, you can use your router as just a switch and access point. In this case, turn off its DHCP server.
Try changing the Primary and Secondary DNS Server in the DHCP settings as below

Primary DNS Server : 8.8.8.8
Secondary DNS Server : 8.8.4.4

Bascially the above DNS servers are provided by Google for IPv4. For IPv6 use these

Primary DNS Server : 2001:4860:4860::8888
Secondary DNS Server : 2001:4860:4860::8844

Maybe this will help You