So, you're afraid you've bricked* your router. Don't worry, there are a number of things you can try to get your router working again before giving up and living with the fact that your router is now a paperweight.
* (A bricked router is a router that you can no longer communicate with through wireless or wired connections.)

Before you continue below, make sure you've first tried a hard reset to revive your router:

1. Disconnect the router from UTP cables (not the power cable).
2. Push reset button for 30 secs.
3. Without releasing reset button, disconnect power cord.
4. Hold the reset button for another 30 secs.
5. Replug the power cord.
6. Still hold the reset button for another 30 secs.
7. Release the reset button and give the router about 10 secs to resettle.
8. Disconnect power cord for another 10 secs and then reconnect.
9. All should be in default settings now.

Recovery by JTAG cable

For the JTAG pin-out see Hardware Info. Then download the Marcin Baliniak's JTAG Debrick Utility.

1. solder the JTAG cable following the above linked pin-out (wiring diagram is attached).
2. solder a 14 pin header on the PCB of the router.
3. to install the giveio.sys copy giveio.sys and loaddrv.exe into {windows}\system32\drivers (*usually C:\windows\system32\drivers*)
4. double click loaddrv.exe in the system32 dir. This is important.
5. append the filename giveio.sys onto the path in the utility
6. press the load button and the start button, they should both confirm success. If this does not happen go no further, go back and fix this.
7. from the command prompt cd to utility's directory and run wrt54g.exe to get a list of options
8. to check your cable, plugin and power up the router and try to backup your ENV: wrt54g -backup:env /fc:29
9. it will then detect the CPU type. If not then check your cable.
10. after you have backed up your environment, follow instructions written in "readme.wag200g" file.

Flashing the KERNEL or WHOLEFLASH will take a very long time using JTAG via this utility.

Note: Do NOT flash whole flash using a standard image file. Use whole flash image prepared for flashing by JTAG.

Note: Router's MAC Address should be changed from Telnet or SSH after flashing whole flash:
echo "maca 01:23:45:67:89:ab" > /proc/sys/dev/adam2/environment

* 01:23:45:67:89:ab is an example. Use the MAC address written on your WAG's rear side.