Press and hold the reset switch for 30 seconds and release.  Now power cycle the router.  Attempt to downgrade the firmware again, but rename the file to code.bin.  If this does not work, go to ftp://ftp.linksys.com/pub/network/ and download the program tftp.exe and run the program.  Input your ip 192.168.1.1, password of the router (admin) and the file name path code.bin.  Once done, power cycle the router and reconfigure it again.