Problem w/ Win NT 4.0 RAS + Win2K & XP

I have a Windows NT 4.0 SP6a Server running RAS. I’ve discovered recently that Win2K and WinXP computer are unable to connect correctly to the RAS Server.

The NT 4.0 RAS Authenticates correctly and registers the presence, but the Win2K and XP Clients freeze at the ‘Registering Computer on the Network’ window. Any ideas or solutions to this problem, as I know someone else has run into.
I double checked all the settings and everything is set as should be.

Thanks.