A break through has been made in the Windows Vista and PAL2.0 issues. For those that might not be aware, Windows Vista does not work with PAL2.0. PAL2.0 uses WPA-Enterprise which uses PEAPv0/MSCHAP. The issue with Vista is that they changed their EAP implementation in such a way that freeRadius does not understand. Currently the freeRadius team is working on a patch but this will take time to create, implement, test, and certify.
You can read one of many threads about this [here].
Until this issue is resolved, I would suggest using PAL1.0 (SSID: PAL) and then VPN'ing into vpn.purdue.edu. If you want higher speeds, I would suggest using the Cisco Client provided on the Airlink page as it uses IPSEC which is hardware decoded. PPTP works but decryption occurs in the CPU decreasing the concentrators ability to perform its administrative tasks.