Whilst running WinXP with a 350 PCMCIA attached, I inadvertently installed Microsoft Upgrade 815485 (WPA Update) and have since been unable to Associate albeit for 5 seconds following card insertion. Roll-back recovery proved that the MS upgrade caused the problem.
Please beware. Ive since found that Cisco are in the process of incorporating WPA support to the Aironet Product line. Let' hope that it includes the 350 series.