Problem with Reset/upload the new program to Arduino Uno Rev3-Main Board

After I've used the Xbee modules for the wireless communication between two Arduinos, and both of the arduinos now are unable to upload new new program or reset it. some says that is the problem from my serial communication port as i connected the Rx(digital pin 0) and Tx(digital pin 1) to my Xbee modules.

// code of sender (Arduino 1)
void setup() {
Serial.begin(9600);
}
void loop() {
Serial.println("H"); //turn on the LED
delay(1000);
Serial.println("L");//turn off the LED
delay(1000);
}

// code of receiver (arduino 2)
char msg = ' '; //contains the message from arduino sender
const int led = 13; //led at pin 13
void setup() {
Serial.begin(9600);//Remember that the baud must be the same on both arduinos
pinMode(led,OUTPUT);
}
void loop() {
while(Serial.available() > 0) {
msg=Serial.read();
if(msg=='H') {
digitalWrite(led,HIGH);
}
if(msg=='L') {
digitalWrite(led,LOW);
}
delay(1000);
}
}

"Don't use pin 1 or pin 0, because these are used to communicate with the USB and thus into the computer.
Just disconnect the circuitry from pin 1 and you should be OK". by Grumpy_Mike http://forum.arduino.cc/index.php/topic,25714.0.html

But i tired to disconnect all the circuitry on my arduino, and it doesn't work as well.....please give me some solution for this....much appreciated for the helpss...