802.11b / ipv6 oddity

[Sascha Luck]

I am running v4/v6 stacks in parallel on my 802.11b network. v6 is provided via tunnel over a DSL connection. AP is a FreeBSD 5.1R box with a PrismII based 802.11b card, the other machines are 5.2.1R/Lucent and -CURRENT/Broadcom(ndis).

The problem now is that every download via ftp/http stalls after 65k on either client machine. Downloads on the gateway box are normal. 
Anything < 65k is normal as well.
The MTU of the tunnel is 1280.(I've tried reducing the MTU on the wireless interfaces, makes no difference)
Has anybody else come across this issue?

Cheers,
Sascha