Continously getting trash from XBee

Hy all!

There're two computers, computer "A" and computer "B".
"A" (receiver, API is the name I think): PC, USB cable, Parallax XBee USB Board, Zigbee XBee Pro Series 2
"B" (sender, AT is the name I think): PC, USB cable, Arduino Uno, Arduino XBee Board, Zigbee XBee Pro Series 2

The problem is if I just connect the Arduino on the "B" side, it will send continously trash throught the XBee to the other side. I think it consist of random values, so I don't think I can filter this. But if I send something real values trought XBee, I will get that too on the receiver side. The baud rate is 9600.

The question is how should I disable the trash, and only receive the normal values?