RS232 Xbee polling

Hello everyone, I am requesting your insights in a problem that I am facing with my setup.
Before I thought about implementing a wireless using Xbee, the current setup looks like this:

(2) Peripheral devices both outputting information in RS232 format > Connected to 4 port USB Hub > One USB connection to PC > Application receives the data
The peripheral devices are set to: Baud rate 4800, POLL

What I have done so far in the quest to implement wireless system.

(2) Peripheral devices both outputting information in RS232 format > Connected to 4 port USB Hub > One USB connection to XBee Transmitter> XBee receiver connected to PC > Application receives the data
The XBees are programmed to communicate to each other. Baud rate set to 4800

USB from the HUB: 4 Pins : Power connected to 5V, Ground connected, D+ connected to Pin 3 (Digital In) of Xbee, D- connected to Pin 2 (Digital Out) of Xbee. The Transmitter XBee sits on DIGI Dev board and gets power from there.

The Receiver XBee sits ona USB adapter board and is connected to PC with USB.
Now, when I run the application that receives data just fine in the Wired mode, it throws an error. I can see the data Communication LED on both XBees flash. What am I doing wrong?

The XBee is a 3V device and not a 5V device. You need a level shifter to connect the XBee to a 5V device such as a USB chip.