Weird proeblem about wifi connection between Macbook and Belkin pre-N route

I replaced my 2 years old Belkin G router by a Belkin Pre-N router (F5D8233) recently and found a weird problem. I can set and connect my Macbook (2006) with the router but can only surf the internet when the AC adapter plugged. If I unplug the AC adapter from the Macbook, the connection between the router and Macbook doesn't loss. But I can no longer reach the internet. Plug the AC adapter again, then I can reach the internet again. Anyone here have similar problem and how to get it over?

Thanks


p.s. My iMac have no problem with the Belkin Pre-N router at all.

Message was edited by: Takenoko