Unable to establish IPv4 connections to neighbour domU domains

[Lars Hoss <lars%woeye.net@localhost>]

Hi all!

We are currently setting up a new box with XEN. Dom0 is powered by a  
modified Debian Sarge.
Yesterday I set up a NetBSD 3.1 domU. So far everything seemed to  
work fine. But then
I noticed that I was not able to connect to other Sarge based domUs  
(Sarge dom0: Sarge domU, NetBSD domU) .
Although netstat says that a connection has been established nothing  
happened. SSH for example just hangs forever.
On my own box with NetBSD as dom0 this problem does not occure  
(NetBSD dom0: NetBSD domU, NetBSD domU).
Maybe there's some kind of incompatability between Linux and NetBSD?

Thanks for your help in advance,
Lars