Wi-Fi not working

I can't seem to connect to the internet when my phone's wi-fi is on. I can get on android market and some of my apps work but when i try to use my browser I get an error telling me to check my network connection. The phone shows up on my routers attached devices list. This is a warranty replacement phone. My first work just fine. Not sure if there is some kind of setting I'm just missing? I'm in a spotty 3G area so when I'm at home i like to use my home wireless network. Any ideas will be greatly appreciated.

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