Hi Nicholas,
Sorry to say it's probably time for a new card
The 350 adapter cannot be upgraded to support WPA2 :( Have a look;
Q. Will Cisco Aironet 350 Series access points and client devices support WPA2?
A. No. Cisco Aironet 350 Series products will not support WPA2 because their radios lack AES support. Customers will need to upgrade to Cisco Aironet Series access points and client devices that support AES if they wish to use WPA2.
Q. What Cisco Aironet client devices will support WPA2 and AES?
A. Cisco Aironet 802.11a/b/g client adapters purchased today can run AES and support WPA2. Cisco Aironet 802.11a/b/g client adapters purchased in early 2005 are AES-ready and need only a software upgrade to run AES and support WPA2.
From this doc;
http://www.cisco.com/en/US/products/hw/wireless/ps430/products_qanda_item0900aecd801e3e59.shtml
Hope this helps!
Rob