pfsync between 8.4 and 9.2

[Pete French]

I just started rolling out 9.2 to all our production machnes, which
are currently on 8.4. We have tested it pretty throughly internally
and are very happy with it, but as part of the deployment have hit
a problem. We have a pair of boxes running as a firewall using carp
and pfsync. One of the - the 'passive' one - has been upgraded to
9.2, and all works fine as far as carp si concerned, but what I have
found is that pfsync doesnt seem to work - i.e. when it fals over existing
connections are not kept live. This works fine when the boxes are both
running 8.4

Of course, I am not sure if fsync is expcted to work across different
OS releases, so my plan was to go ahead and upgrade the other box
on the assumption that when they are both running 9.2 it all will
start working again. But I thought I shiuld mention it here
to see if anyone has seen simila, or to see if anyone says "hmm, it
should work fine between 8.4 and 9.2"

so, any thoughts ?

-pete.