What are you using for the DHCP server for the PPTP network?  If you are 
using the m0n0wall for this:  The DNS servers entered in System: General 
setup <https://m0n0wall/system.php> (or the DNS forwarder 
<https://m0n0wall/services_dnsmasq.php>, if enabled) will be assigned to 
clients by the DHCP server.  The PPTP "Server address" will also be 
added as a DNS server... thus the DNS lookup will still hit the 
m0n0wall.  Unless of course you are redirecting the PPTP connections to 
another PPTP server.

Brian Morton wrote:

> I have figured out the issue, now I just need to figure out how to fix 
> it.
>
> By default, m0n0wall only includes a rule to allow TCP traffic from 
> the PPTP
> clients.  Since DNS is a UDP protocol, all DNS lookups from PPTP clients
> were being blocked.  I added a rule to allow all UDP traffic over the 
> PPTP
> interface, and this resolved the issue of being able to resolve names.
>
> Unfortunately, it appears Windows XP tries the local DNS servers for my
> network interface before trying the one on my PPTP interface.  This means
> that when I try to resolve a hostname on the m0n0wall network, it first
> attempts my primary local DNS server, which is a public DNS server for my
> ISP.  This lookup fails, and it assumes that the host does not exist.  Is
> there any way to make the DNS server served by the PPTP server take 
> priority
> over my local DNS?
>
> On 2/12/07, Lee Sharp <leesharp at hal dash pc dot org> wrote:
>
>>
>> On Mon, 12 Feb 2007 14:44:36 -0500
>>   Brian Morton <rokclimb15 at gmail dot com> wrote:
>>
>> > I am running 1.23b3 pc-generic on a PII 300 with 128MB RAM.  This is
>> >my first set up at this location, so I can't say if this feature
>> >worked prior to this version.  I have the option set to "register
>> >dhcp leases in DNS forwarder".  In my prior experience with m0n0wall,
>> >this should cause a Windows computer name to resolve to the internal
>> >ip address (for instance, a computer named "brian" should resolve to
>> >an internal address when "brian" is pinged).  This does not seem to
>> >be the case when I connect via PPTP.
>>
>> Do an "ipconfig" on the machine you are tunneling in on.  I bet your
>> DNS is NOT the remote m0n0wall.  And it will need to be to find those
>> names.
>>
>>                            Lee
>>
>