Slow wireless internet, and fast wired internet

Hello,
I'm new to this forum.
I've a macbook (end 2007) with Leopard, and a home wireless network (netgear wireless G router). when i'm using the wired connection, the internet is fast (about 2.8 MBps). But when i'm using the wireless connection, the internet is very slow (about 400KBps).
I've updated my router firmware (put the most recent one) and checked all the router settings.

I have the same probleme when running windows XP on bootcamp.

Can anyone help please?

Note: I measured the internet speed using speedtest.net

Superdelphinus said:

Do you live in a nuclear bunker

Click to expand...

What do you mean? is that a joke?

kingjr3 said:

He's suggesting that you may have interference over the air. Try changing channels on your router...

If that fails, try a different router.

Click to expand...

Thank you, i've already tried to change the channel, and it doesn't help.
I'll try my macbook in another wireless net.