WPA encryption problem

Hi all,

I'm having some problems with my wlan.
Until now I used WEP encryption, and all was going just fine.
Now I would like to switch to WPA-PSK encryption.
All hardware is supporting this, and all drivers are up-to-date.
The AP configured for WPA-PSK, I tried to setup my PC (windows XP). Entered the passphrase, and the result is the following :
Wireless connection is good (green icon...), but the PC does not receive its IP address.
I did not tried yet to manually setup an IP; and honestly I would prefer to have this setup automatically like before.

Any idea ? Thanks for any feedback

Just noticed that giving a static IP, will change continuously the status from "connected" to "out-of-range".
Also, I unchecked the Windows Firewall for the wireless card (Advanced Tab).