Windows 7 can't map NT Share through VPN connection

I am able to succesfully connect via VPN (Sonicwall TZ100) and map all my XP & NT network shares with windows xp so I know that much is working.

Now when I try the same procedure using windows 7 home & pro I am able to establish the VPN connection,  map the shares on the  windows XP pro machines, that portion is fine. When I try to map to our older NT 4.0 SP6 machine, from the cmd window  I am prompted for the username and password combination. I enter the correct combination and windows spits back "System error 86 has occurred. The specified network password is not correct". I am able to ping the NT server and it responds with no problem. It must be some setting withing W7 thats not compatible with NT but I cant figure it out.

If I am connected directly to the local lan where the NT server resides I can map without any problems.

Any suggestions?

J Anderson