it's alive, it's alive! pressed the reset button for a couple of hours and it magically worked again. lol!
^luckily, linksys has a recovery mode you can use in case of disaster happens during upgrade process, like what happen to you.
use the usual tftp recovery.<click here for link>
already did that (see no. 4) but it didn't work because my pc can't communicate with the router (unpingable). thanks anyway.