After doing a quick google search for a copy of the instruction manual...I assume this is the device- http://www.dd-wrt.com/phpBB2/download.php?id=21995&sid=79c0e542a2f3d7e2f7005487564555d9.
If it is; after flicking through it, I can not seem to find any information on whether or not it's possible. One way to fix this is by checking on the DD WRT website if there is any of their latest firmware for this router, flashing it to the device by going to page 116 then following the standard DD-WRT guides that are everywhere online.
I'm sorry I couldn't be more help.