Yes, this was the case. Thank you! I am using a singleton (http://rosettacode.org/wiki/Singleton#ActionScript) to act as "shared memory" between the subapps. I was setting singleton.addEventListener(someType, listener) in subapp A's creationComplete callback. So everytime I navigated back to A, the creationComplete was running and re-adding this listener. After the search, the listener method (that opened the popup) was being called multiple times, i.e., as many times as the event had been added.
Thanks a million!
Message was edited by: istrasci - Having trouble editing the link, so putting it in directly.