FreeBSD 5.4 802.1q and linux stalls

[Meno Abels]

Hello,

i have here a very strange problem which is in real a linux problem
but it is triggered by freebsd. I run a lan on which are linux 2.6.8(debian) and
freebsd 5.4 systems are connected to a unmanaged gigabit switch. All systems
uses this gigabit adapter:
 Realtek Semiconductor Co., Ltd. RTL-8169 Gigabit Ethernet
Everything works fine until i do on one freebsd box the following:
 ifconfig vlan0 172.20.21.1 netmask 255.255.255.0 vlan 2 vlandev re0
i just do this, there is nowhere any configuration for  802.1q  on any other
machine on this lan. 
What is happen now the freebsd continues to run without any problem, but
all linuxs are stopping to understand any arp responses from a freebsd
nor an other linux.
So they stop to work over the time on this lan anymore. If I do
"ifconfig vlan0 unplumb"
it takes up to 10 minutes and the linux's are return to the working
status as before
the ifconfig vlan0... 
I didn't not have any clue which network packet could cause these behavior in
a linux but there has to be one. Does anybody as any idea?
On that lan there is UDP-Broadcast(spread) and multicast traffic(ganglia) 
also there are around 120 carp addresses configured on the 10 freebsd boxes.
Everything else is standard tcpip/nfs traffic. There is no firewall
rules on the interfaces on thes linuxs or the freebsds.

thanks alot

meno 
P.S. don't ask why i'am try on 802.1q it has something todo with the very
high amount of the spread traffic which i try to seperate from some
vpn tap/ethernet
brigde interfaces.