if_bridge hangs server

[Andrea Venturoli]

Hello.

I hope someone can help me with the following problem...
The box runs a 8.3p7/i386 and has three physical ethernet interfaces: 
em0, em1 and fxp1.
em0 and em1 are bonded into lagg0, over which carp0 and carp1 run.
fxp0 has three vlans: vlan1, vlan2 and vlan3, over which there are 
respectively carp3/carp4, carp6/carp7, carp9/carp10.

To make it clearer, here's the extract from my rc.conf:
> cloned_interfaces="lagg0 vlan1 vlan2 vlan3 carp0 carp1 carp3 carp4 carp6 carp7 carp9 carp10"
> ifconfig_em0="up"
> ifconfig_em1="up"
> ifconfig_lagg0="laggproto lacp laggport em0 laggport em1 192.168.101.1 netmask 255.255.255.0"
> ifconfig_carp0="vhid 1 pass xxxxxxx 192.168.101.10"
> ifconfig_carp1="vhid 2 advskew 200 pass xxxxxxxx 192.168.101.10"
> ifconfig_fxp0="up"
> ifconfig_vlan1="inet xx.xxx.xx.xx netmask 255.255.255.248 vlan 4 vlandev fxp0"
> ifconfig_vlan2="inet xx.xxx.xxx.xxx netmask 255.255.255.248 vlan 2 vlandev fxp0"
> ifconfig_vlan3="inet 192.168.2.201 netmask 255.255.255.0 vlan 3 vlandev fxp0"
> ifconfig_carp3="vhid 4 pass xxxx xx.xxx.xx.xx"
> ifconfig_carp4="vhid 5 advskew 100 pass xxxxxxxx xx.xxx.xx.xx"
> ifconfig_carp6="vhid 7 pass xxxxxx xx.xxx.xxx.xxx"
> ifconfig_carp7="vhid 8 advskew 100 pass xxxxxxxxxxx xx.xxx.xxx.xxx"
> ifconfig_carp9="vhid 10 pass xxxxxxxx 192.168.2.203"
> ifconfig_carp10="vhid 11 advskew 100 pass xxxxxxxx 192.168.2.203"



Now I need a tap based OpenVPN, so, per instructions I have found, I run:
> ifconfig bridge0 create addm lagg0 up

After the above command is issued, the box won't live for other five 
minutes; everythings works fine as before, but the server will soon 
hang: no crashdump, no message, no reboot, just a sudden freeze. The 
only way to restart is the reset button.

So I'm stuck and don't know what to do.
Are there any known issue regarding if_bridge which I might be encountering?
Anything related to if_bridge interaction with carp, vlan or lagg?
With ipfw?
Any hint on how to debug this?
Would an upgrade to 9.1 help?

  bye & Thanks
         av.