I'm guessing you don't have an oscilloscope to simplify this.
Next step: disconnect the Arduino, and connect the router Rx to its own Tx by shorting the wires you were using to connect to the Arduino, at the Arduino end. That will tell you whether you have a problem like a damaged component or bad solder joint.
i'm trying to built a wifi robot car with my arduino but can't seem to get any success in letting them talk to each other
i followed jbprojects and used a max232ecpe in my router isn't this the problem or can i leave it out it would be much simpler if i could connect them directly with resistor
I already have 2 wrt54g's
one for my actual internet and 1 to create the robot
if bridged i can use my ln-400 ip camera to stream video
I wonder if its easier to use serial communication
OR
set the WRT as a bridge and use a Ethernet shield to create a web interface that controls the servo and motors
I suggest first you connect the tx/rx pins on your robot router and see if you can get an echo back from that router using the other router to connect. When you successfully do this, then you can start looking at connecting the robot router to another device like the arduino.
By default (actually, more dependent on which OS you put on the WRT), one com port is interactive... the other is like a syslog output printer or monitoring port.