vista - keep needing to restart dns service

> As per the title, I'm using 64-bit ultimate in a 2003 domain. Brand
> new install and I've noticed that frequently (talking 3-4 times a day
> here) the DNS service appear to suddenly stop being asked to perform
> lookups. The service itself never appears hung or stopped, but
> wireshark suddenly reports broadcast being used to look up hosts
> instead of DNS.
>
> As soon as I restart the DNS service, normal service resumes.
>
> I've also installed the ISA client and it's the same operation. Trust
> me, my network settings are correct
>
> It's as simple as :
>
> c:\>ping testmachine
> Ping request could not find host testmachine. Please check the name
> and try again.
>
> (wireshark shows broadcast)
>
> c:\>nslookup
> Default Server: ourinternaldnsserver.x.x.x
> Address: 10.40.x.x:53
>

> > testmachine

>
> Server: ourinternaldnsserver.x.x.x
> Address: 10.40.x.x:53
>
> Name: testmachine.x.x.x
> Address: 10.40.2.7
>
> (wireshark shows proper DNS query and result as expected)
>
> c:\>ping testmachine
> Ping request could not find host testmachine. Please check the name
> and try again.
>
> (wireshark shows broadcast for name lookup)
> (restart DNS service)
>
> c:\>ping testmachine
>
> Pinging testmachine.x.x.x [10.40.x.x with 32 bytes of data:
>
> Reply from 10.40.x.x: bytes=32 time<1ms TTL=255
> (wireshark shows dns lookup, followed by icmp)
> etc.
>
> (Note that this isn't a DNS postfix issue, results are the same
> whether the full domain name is specified or not). Also, by and large
> the reason that broadcast don't return an answer is that I'm going
> across routed nets, and also frequently to unix hosts.
>
> Any ideas? It's enough to be annoying. Have been googling for a while,
> no joy as yet
>
> Thanks
>
> AW