Well... if you brick your router you have at least one last chance to recover it
Oh... by the way... be sure you have tftp client and a working firmware ;)

1. Start your Asus WL-600g keeping the reset button pushed


2. Force your network device to one IP in 192.168.1.2-192.168.1.254 range (note: you have to be wired-connected to the router)


3. Start your ftp client (you will have a "tftp>" prompt)


4. • tftp>[just press enter a couple of times...]
     
   • tftp> verbose
     Verbose mode on.
     
   • tftp> trace
     Packet tracing on.
     
   • tftp> rexmt 1
     
   • tftp> binary
     mode set to octet
     
   • tftp> connect 192.168.1.1
     
   • tftp> put WL600g_1.0.3.3.A.trx
     
     .....[ now you will receive a lot of the following messages].....
     
     sent DATA
     received ACK
     sent DATA
     received ACK
     sent DATA
     received ACK
     sent DATA
     received ACK
     sent DATA
     received ACK
     sent DATA
     received ACK
     sent DATA
     received ACK
     
     .....[ then some more messages].....
     
     sent DATA
     received ACK
     sent DATA
     received ACK
     
     .....[ then it should finish :) ]
     


5. Reboot your router keeping your finger crossed

Note: your router configuration MAY be restored to the original one (not always)