Samba with PPTP

Hi

I am running samba on a freebsd box (behind NAT, IP = 192.168.1.207) with
pptpclient connecting to my company m$2k VPN (tunnel IP = 192.168.0.206).
At first, I can ping the fbsd with its hostname (freebsd) from my company.
But when I try to "net use freebsd /user:xxx *", the "net use" will fail
(err = The network path was not found.) and afterwards I can see that ping
will use 192.168.1.207 (which was originally 192.168.0.206). I can ping
again if I restart the samba. But everytime when I try to use the netbios
name I will get the redirection changed wrongly.

So I tried to use IP instead. I can browse \\freebsd and "net use" my home
\\freebsd\ivan sucessfully. But when I try to browse \\freebsd\ivan it will
hold for a minute and I will finally get the message \\192.168.0.206\ivan is
not accessible. The specified network name is no longer available.

Thank you.