Soundcast

Greetings from Perth, Western Australia. First of all, congratulations on yet another outstanding product!
We took stock of the OutCast Jr yesterday, and are very pleased with it. The only concern that has arisen is this: when we had our store's iPod in the old transmitter, it sent a signal to both the original OutCast and the Jr, however when we plugged it into the new transmitter, it would only send the signal to one or the other, even though they are both set to the same channel. We switched it back to the old one and lo and behold, it sent the signal to both. This test was done with only one transmitter powered at a time, so it wasn't a cross-talk issue. Any ideas?