What is the build number on the one that worked for you? I have heard that 13535 worked, but it looks like you might be using 14684. Please confirm the build number that is working for you.
I think it is despicable that Buffalo is selling these units as DD-WRT ready, when in reality, most of the functionality that is off the beaten path for routers flat-out doesn't work with DD-WRT. Buffalo, if you care, you need to get your buns down to wherever the good people making DD-WRT live, and have a conference with them in which code is written, analyzed, and tested until you have a 100% working DD-WRT for Atheros.
Either that, or go back to Broadcom chipsets going forward and offer to exchange all the Atheros units free of charge.
I know this: Linksys equipment hasn't looked so attractive to me in years.