CC2430EM Coordinator receive from multiple devices

I'm having trouble wih my Zigbee coordinator receiving from multiple routers. I am running the SerialApp and attempting to send characters over a terminal from 2 PCs with attached RF04EB and CC2430EM boards. I can receive from one but in order to receive then from the other I have to send around 5 or 6 characters before I start to see it on the coordinator's side. Then this process is reversed and I get the same thing. I remember reading somewhere about the sample apps you can't have more than so many devices communicating with a coordinator at one time but is that correct? Is there a define in code or a config file I've overlooked to get the coordinator to receive from multiple devices, specifically routers? Thanks!