Failparty.

Hi all..
Here we go.. My problem:
In school we've got a wireless network secured by WPA.
By knowing the right people I got the key to get into it and
I can successfully connect with my HTC Desire. Same with my
iPhone 3G. The problem is, I havent got access to the internet.
But a friend of mine has got access to the internet at the same SSID
with the same key.The only difference is that he uses an iPod Touch and
has got access since at least one year.
To determine if there's a MAC filter I took my notebook to school and
spoofed (with a Linux OS) the MAC adress of the WiFi adapter to the one from the iPod Touch. As result I hadn't internet at all. Fail.
Now I'm asking myself why I still don't get internet access while this damn iPod does. Also I tested wether I get connection to the router by pinging it and yes, there is an excellent connection. The router is a Dlink router.
Has anyone got an idea? I'm really suffering from this thing..

Greetz,
Mr. Niko