I am sorry to say this, but in order to do AES with the AP you are using, you MUST have either an AIR-RM21A or AIR-RM22A...this ap does not have either one of these radios.
...the following excerpt is from the 12.3(2)JA release notes:
This feature supports Advanced Encryption Standard-Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (AES-CCMP). AES-CCMP is required for Wi-Fi Protected Access 2 (WPA2) and IEEE 802.11i wireless LAN security. This feature is not supported on 350 series access points.
This feature is supported on these devices:
•1100 series access points (802.11g radio only)
•1130AG series access points
•1200 series access points (IEEE 802.11g and 802.11a radios only with the part numbers AIR-RM21A or AIR-RM22A)
•1230AG series access points (IEEE 802.11g and 802.11a radios only with the part numbers AIR-RM21A or AIR-RM22A)