Do "show ap-group "Admin Office"" and note the 802.11a radio profile and 802.11g radio profile in use. Then, do "show rf dot11a-radio-profile <name>" and "show rf dot11g-radio-profile <name>" (where <name> is the name in use above). Are they using the same ARM profile?
Then, do "show rf arm-profile <name>". Is the ARM profile for the dot11g radio profile set to allow only 40MHz channels in the "a" spectrum?
If things still look right, check the software version. I haven't seen any bugs like that, but it may be possible.