Probably you have a version with 4 MB of RAM. You need the firmware from here:
For the initial flashing(from factory firmware) please use this firmware:
http://dd-wrt.com/dd-wrtv2/downloads/others/eko/BrainSlayer-V24-preSP2/2013/07-24-2013-r22118/broadcom/dd-wrt.v24_mini_generic.bin
Regards,
Steve Hars,
Hotspotsystem.com