I just noticed that the german site has a new firmware available at ftp://ftp.dlink.de/dap/dap-1522/driver_software/DAP-1522_fw_RevAll_v1.22_rc029-2010-09-08.zip
I flashed it and everything works as expected when using it as an AP.
Before flash:
Current Firmware Version : 1.21
Current Firmware Date : 11:36:48 06/26/2009
After flash:
Current Firmware Version : 1.22
Current Firmware Date : 11:03:25 09/08/2010
I found this when trying to change the US firmware to Europe firmware to enable channels 12 and 13, but I was unable to do this. Is this a hardware limitation?