Yes this possible.
11N Hardware is designed to use WPA(2) with AES encryption. This is implemented in the chipsets.
WEP is no longer part of 11N standards, it is only for downwards compability.
DIR and DAP are connected with 54 Mbit legacy mode if you use WEP.
From setup/wireless menu:
If you choose the WEP security option this device will ONLY operate in Legacy Wireless mode (802.11B/G). This means you will NOT get 11N performance due to the fact that WEP is not supported by the Draft 11N specification.