I am having the same, or similar problem. I bought a Wave SoundTouch Music System IV, a SoundTouch Link Adapter (connected to the Aux In on my reciever/amp, and two SoundTouch 10 Wireless Speakers. When I get a streaming FM signal on one, then try to get them all playing the same streaming station (home Wifi connected), they are all out of synch.
I can get any, and all of the speakers and main system on, and streaming the same FM channel, but they are all out of synch by anywhere from a few seconds to 1/2 a minute. This is very frustrating, as the Bose system is what my wife really wanted, throughout the house, but I can't get it all to synch and now feel I've wasted well over $1,200!