One thing we are noting is that if we are using a machine (someone's home) which has never been on the domain it appears like Windows security is not retained or passed on by the ASA. For example we get in via VPN and try and go to \\server1\folder1 and you get the windows authentication page but which works but you still are locked out of the folders. Same things happens when you go to \\server1\c$.... We can get to secured web sites but again it will always ask for authenticate.
With PPTP once authenticated the security passed on to other systems on the other side so we didn't see this issue.
Any help would be appreciated. Thanks in advance!