Firstly I apologize for coming back to you a bit late.
Is it that the XBees are taking time to communicate with each other? What kind of XBees are they? How are they configured?
The Xbees are :
XBee Pro 60mW Wire Antenna - Series 1
Bothe Xbees are configured using XTC-U.
The Xbee on the car is configured as a Coordinator, set to broadcast the information(i.e. the Destination address low byte is "FFFF" and the high byte is zero). It is configured to have a Packatization timeout of 0xFF. It has the baud rate 19200 bps.
The Xbee connected to my laptop is configured as an End Device, and it's PAN ID and baud rate match the Coordinator.
Let me know if you need to know any other specific parameter as there are quite a few.
tell us what kind of shield you are using
On my shields it is written:
"Arduinoxbee v1.1"
Underneath that it is written "M.Yerze".
I apologize again for coming back to you late and certainly appreciate your guidance. I am not sure about the answer to the rest of the questions that you have asked and I have not had the chance to test what happens when I increase the baud rate on the Uno and Processing, as we discussed previously. I will let you about that as well as soon as possible.