[c-nsp] mac flapping on 6509 between core and fwsm

[ryanL]

does anyone know what would cause this? po30 uplinks to a core router,
and po579 is the internal etherchannel assignment for the fwsm. the
fwsm is bridging. the 6509 is spanning-tree root for the vlan. vl1250
is the outside interface. the mac in question is core router,
configured as po30.1250. the core has numerous other subints
configured the same way (so, same mac), but only this vlan reports the
move, repeatedly.

%MAC_MOVE-SW1_SP-4-NOTIF: Host 0024.f716.5142 in vlan 1250 is flapping
between port Po579 and port Po30

6509 vss is running 12.2(33)SXI6
fwsm is 4.1(7)

i have multiple fwsm contexts configure the exact same way (diff'd),
and i don't see this issue.

appreciate any clues.

ryan