You could try the old 30-30-30 reset:
Hard Reset (aka 30/30/30 reset):
The following procedure will clear out the NVRAM and set dd-wrt back to default values:
1) With the unit powered on, press and hold the reset button on back of unit for 30 seconds
2) Without releasing the reset button, unplug the unit and hold reset for another 30 seconds
3) Plug the unit back in STILL holding the reset button a final 30 seconds, then release the button