Search Google for framemaker text flow, framemaker parallel text
flows, and similar terms. There was a discussion of the problem on one
of the public FM lists or forums. One issue was that the old method of
incorporating a tiny frame of one or the other flow on left or right
master pages no longer worked. I'm not sure if the change occurred in
FM 6 or 7, or if this applies to your problem, but it's worth a bit of
search time. Perhaps other relevant topics will result.