Using a Samba PDC as the password server for an Intranet solution

[sni]

I'm currently working in a project that aims to create an intranet.
We are using a standalone NT-server as the web server, and a Samba
machine as a PDC for the domain in which the web server participates. 

Besides the trouble with actually getting the NT machine and the Samba
PDC to accept eachother and let the web server be part of the domain, I
have encountered some small difficulties. The system now handles around
4000 users, who all have their own entities in the smbpasswd and the
passwd file on the Samba machine, which by the way is a SUN box. 

I have successfully managed to set up the configuration so that the
samba PDC validates users that log on to the NT web server, which
actually seems to work really well. However, when I want to set the
access permissions for a certain directory in NT and bring up the user
list to select users that should be granted access, an error occurs and
is displayed in the NT dialog box saying:

Unable to browse the selected domain because the following error
occured: 
Invalid access to memory location

The only things I get in my samba log are some:
getsmbfilepwent: malformed password entry (no terminating :)


What I want to know is whether this is a misconfiguration error or if it
is not possible to use the Samba PDC like this?

Regards

/Staffan