Macbook can not surf internet via google chrome and safari, but internet works properly

I have a Macbook 3.1 white, currently running Snowleopard 10.6.8. I upgraded my system to 10.6.8 and the RAM to 4g half an year ago. It works very well without any problems. However, Last night, after I updated two things (one is Safari and the other one I couldn't remember), suddenly My MB couldn't access to any website anymore, including google, gmail, bbc etc.

I was wondering the wireless not working, so I restart my rooter. Still I couldn't open any website, though wireless indicated it is connected. My housemate tested the internet which is fine by his laptop. Suprisingly, my Skype works well-- I can use it to do a voice chat (I confirm it again by using another chatting software). Therefore, I guess, the internet connection works but not for the internet explorers. It is really funny! Anyone has the same issue or not? Any suggestions to figure it out?

Thank you for your helps!