Virtual Serevr R2 guest no network ?

I just installed VS2005R2 and installed q windows 2008 as guest OS. configured the network connections – virtual networks etc and all seem fine.
the problem is that i cannot ping outside of the guest os, not event the GW ! whereas the GW is accessible from outside.
i have been told that the switch port is using protection mode ot accept on,y 1 MAC add. so how do i get this towork ? here is what my hosting support told me :

That is likely because we restrict each switch port to accept only one MAC address.
Most modern OSes have the ability to disable arp flux when using a software bridge. Please consult your favorite search engine for further information.