ADC data

I am currently using 2 xbees with plans of using 8 to sample three channels of data using the ADC and send that data back to a central collector (PC). When doing this, I seem to be getting an extra byte or two of data being inserted into my packet which is throwing off my calculations. It does not happen when I only use one xbee, just when using multiple. It also seems that the extra bytes are zeros. When looking at the X-CTU screen, I will occasionally see some extra white space which could be the culprit, but how do I fix this? I need these extra bytes to go away and there is no pattern so I can’t just manipulate the data. Any thoughts or suggestgions?