Can't access two websites (everyone else can)

I'm currently trying to access two game sites (www.travian.us and www.tribalwars.net). A week ago, I could access these websites just fine. Then all of a sudden, my computer won't even connect to both - just sits on "Looking up: tribalwars.net..." I'm currently on a wireless network with five other computers and two computers connected directly into the router. I'm the only one on the network that goes to these sites, however, no computer on the network can access either site. I can access the websites at friends' houses and through proxy sites (via my computer) such as proxify.com.

I've restarted the router, ipconfig /flushdns, ipconfig /renewip - all didn't help.

What's going on here?