Annoying unstable WiFi problem

Hi all,

So I have this unstable WiFi problem. I have a 2010 MBP, running on 10.6.8.

Symptom

1. Adium connected to Yahoo Messenger randomly being unresponsive, means even I try to send message to myself, it might not come. Message from other ppl sent to me get duplicated. It could get responsive back for a while then unresponsive randomly.

2. I was playing SC2 and constantly get lost connection while searching for player. It is perfectly fine when playing game. I notice if I keep the connection busy by chatting with friends, it won't happen.

So I guess the connection get drop out when I'm idle. Webpage loading is perfectly fine. I don't use Airport Extreme.

What I tried

1. Install fresh Lion - still happen.
2. Install fresh SL 10.6.3 - still happen.
3. Update to latest 10.6.8 - still happen.

The weird thing is my friend running on Windows connected to the same router appears to be just fine.

I'm calling for your help as I was spending more than 6 hours trying to install and re-install all these stuff.

Thanks thanks thanks =)