Atheros and SIS bridging problem

Hello,
 
I'm working on a FreeBSD-based bridge with one Atheros 5004X (5212)
wireless interface and one SIS Ethernet interface.  The Atheros
interface is associated to an access point running hostap (another
FreeBSD box) while the Ethernet port is connected to my laptop. 
Here's a quick outline:
 
[Laptop]--------(sis0)-[FreeBSD Bridge]-(ath0)--------[FreeBSD AP]
 
There seems to be a problem with bridging ath0 and sis0.  I have 1 IP
assigned to ath0 which is 192.168.1.3, and I've sysctl'd
'net.link.ether.bridge.enable=1' and
'net.link.ether.bridge.config=ath0,sis0'.  From the bridge, I can ping
the AP (192.168.1.1) and the laptop (192.168.1.5).  However I can't
ping from the laptop to the AP or from the AP to the laptop.
 
When I sysctl net.link.ether.bridge.debug on, I notice something
strange.  Packets to and from the AP have a destination of BDG_UNKNOWN
until the bridge shows 'bridge_in: new addr xx.xx.xx.xx.xx.xx at 3121
for ath0'.  At that point, I'm able to send and receive a few packets
through the link, but it's very inconsistent.  However, the bridge
debug info now shows the proper interfaces as the destination.  This
only lasts about 20 seconds until I get a 'bdg_timeout: flushing stale
entry 3121' at which point everything gets forwarded to BDG_UNKNOWN
again and no traffic gets passed.  Wtihin a few minutes I get the
'bridge_in: new addr' message again and the cycle repeats.  The amount
of time seems to vary, though.
 
I've tried this on current, 5.3 and 5.2.1.  The wireless interface is
configured without WEP and I've tried 11b and 11g mode.  The AP is a
5.2.1 system with the same type of Atheros card in non-bridged 11b
hostap mode.  I can't think of any additional debug info other than
the bridge debug output, so please let me know if there is anything
else I can supply to help troubleshoot this issue.  Also, has anybody
successfully set up a bridge like this in the past?
 
    Best Regards,
    Ben Becker