freebsd stable - Apr 2011 - Latest STABLE appears to break IPv6 CARP (and other oddities)

I updated to STABLE yesterday to get the net hast patches - all seemed fine,
so I went round and upgraded all the machines. But since then have been
fighting with some odd network issues - to the point where I have rolled
back to an earlier kernel to fix them.

The main issue for me appears to be that CARP under IPv6 broke. It seemed
to work fine (interfaces failover properly) and behaves fine
under IPv4. This is a pair of machines which are actin as a firewall - so
there are CARP interfaces on the outside and the inside.

On the inside, none of the machines can ping the CARP IPv6 address.
TAs this is their default gateway, this means they lose connectivity
to the outside world. Another effect I have is that the firewall machines
cannot ping any aliased IPv6 addresses on the other boxes - I add an
alias to an interface, and the orignal address can be pinged, but the
alias cannot.

So I rolled back to an earlier kernel - I now have working IPv6 connectivity
again via CARP. But I have left the rest of the machines on yesterdays
kernel, and there are still some oddities with networking - the aliased
address problem on one of the machines is not working.

The cusrious thing is, on the ourside (where the downstream machines are
Cisco routers) then CARP worked fine with the upgrade. Itr is only when
talking internally to other FreeBSD machines that I see problems.

Anyone have any ideas ?

-pete.