This is true for all DD-WRT firmware after r15760. Here is a link to the trouble ticket with an explanation and the fix, which is the same as the one you mentioned in Dmitry's original post:
http://svn.dd-wrt.com:8000/ticket/1868
Unfortunately, the trouble ticket is in "closed: wontfix" status, so everytime you do a firmware update on your WZR-HP-G450H, you will need to re-enter the fix. What's really bad is that, before I found the fix, I called Buffalo support and they were completely clueless about both the problem and any way to fix it.