When I first joined the server, I got the error "Can't resolve host".
I figured if I get this error, I couldn't be the only one!
Therefor here a quick and easy guide to resolve this issue!
Step 1.
Open your control panel and go to: "View network and tasks"
http://i.imgur.com/luqWbqO.png
Step 2.
Click on ethernet ( the connection you're using)
http://i.imgur.com/WiCakg0.png
Step 3.
Click on properties.
http://i.imgur.com/WdgdLtU.png
Step 4.
Select "Internet Protocol Version 4 (TCP/IPv4)" and click properties
http://i.imgur.com/e2ZhRWG.png
Step 5.
At the second column you want to select the option "Use the following DNS server addresses"
Enter at "Prefered DNS Server" the following: 8.8.4.4 (This is the public google DNS server which I'm using at the moment).
At last, tick the option "Validate settings upon exit"
http://i.imgur.com/rNIbAav.png
When you've followed these steps, click OK, restart your FTB client and it should work!