xbee communication problems

hello to everybody in the forum. I've a communication problem with xbee and i hode that you will help me.

The configuration is the following: - Coordinator: PC+usb xbee adapter + xbee series 2 pro - End Device: arduino uno + xbee shield + xbee series 2 pro

When I press a button on a keypad, the arduino send a set of integer (8 numbers)

with serial.write command plus a delay(500) between each other.

On the PC (coordinator) run a c# script that simply wait on serial port for the

data coming from the usb xbee adapter.

My problem is that: - sometimes the set of number doesn't not arrive complitely (often 5-6 of the 8

numbers). -sometimes nothing arrive on the serial port.

Obviously if I connect the arduino directly to the PC with USB cable, without

using xbee, all work good, that is the set of number arrive to the pc without

problems. So, the problem is not due to the c# scripts not to the arduino sketch, but on

the xbee communication.

Maybe it could be due to the sleep mode of the xbee? could be due to some kind of reset on the end device?

Someone could help me? Have you some suggestions for me?

Is there any way to disable the sleep mode? When I try to set on XCTU the parameter SM (sleep mode) = 0, it doesn't

work...in fact each time i Read the parameters from the xbee, that SM parameter

is always set to 4 even if I have changed and Write it on the xbee.

Thanks to everybody