[Q] Wifi only working within 6 feet of the router, need help

I've been using Galaxy Note on ICS 4.0.4 for 1 month with no problem. (Bought it form sister in-law)
Started downgrading to GB, root, install CM9 and then CM10.1.
Then I notice the wifi not functioning beyond excellent coverage.
GNote works fine within the area.

Tried connecting to wifi near the router, no data/internet once moving beyond the 6 feet from the router.
The GNote still detect the signal (Good, poor) and the surrounding wifi signal but no data/internet.
Other phone (iPad, iPhone 4S, Lumia 800) still function normally even in the poor area.

Rebooted the router a few time.
Since other device is functioning, I don't think it's the router.
GNote can still detect the signal until quite far away, but no data/internet.

Tried flashing CM10.1 a few time.
Tried flashing CM10.1 + Philz kernel.
Tried Ultimate N7000 Rom.
Downgrade to stock ICS 4.0.4 + Philz kernel.
Downgrade to stock JB 2.3.6
Upgrade using Kies to ICS 4.0.4. Still the problem is there.
Install Busybox, fxr wifi fix... nothing.

I'm out of ideas to find the solution.