Vista - NAT and domain joined VM's

Hi,
Wondering if other folks have had a similar problem (described below)
and if there is any workaround.

My host is domain joined (Vista) and my guest (XP) is also domain
joined. I have signed in using my domain credentials to both the host
and the VM. I have configured my VM to use NAT (only). When I am at
work, I don't face any issues when accessing the net from both the
host as well as the guest. However when I get my laptop home
(hibernate/shutdown the host), I am not able to access the net from my
guest (over home wireless) - again no issues faced when accessing the
web from the host. I have tried restarting the host and the guest
multiple times but the problem persists. The VM acquires an IP
address (no surprise) but I am not able to browse the web (or access
mail for that matter). Tried multiple browsers as well but same
result.

However if I now configure my VM's network setting to bind to the
Wireless NIC I am able to browse the web from within my VM.

Furthermore, I also have another XP VM which is non-domain joined and
which is configured on NAT - I am able to access the web from both
home and work on this VM.

I am not sure if there is some GP or some policy which is resulting in
this behavior - any pointers would be helpful. Thanks