I expected there to be all sorts of information on this problem, but I've yet to find any discussion about it, so here goes:When a VPN connection is established in Vista, it seems that your current credentials change such that establishing a new connection or re-establishing expired (timed-out) connections will fail unless you explicitly provide your user credentials to the shared resource.Example:DOMAIN1\USER3 is logged in to machine DOMAIN1\PC5 and has drive X: mapped to \\SERVER2\SHARE (SERVER2 is also a member of DOMAIN1).The user then establishes a PPTP VPN connection to a remote network using credentials valid on that domain, DOMAIN8\USER4.Even if no connections are made to resources in the remote network (i.e. only the VPN session is established, nothing else is done with the remote network), the user is no longer able to establish a new connection to DOMAIN1\SERVER2. Attempting to map Z: to \\SERVER2\SHARE3 will result in an "Access Denied" error unless the user provides his DOMAIN1\USER3 credentials explicitly.Even more annoyingly: when the EXISTING drive mapping (X: to \\SERVER2\SHARE) times-out due to inactivity (I think this is 5 or 10 minutes by default), Vista will fail to automatically re-connect the mapping as it normally would. In order to use drive X: after it has timed-out, the user will have to first disconnect X:, then re-connect it providing his DOMAIN1 credentials explicitly.I connect to and disconnect from a variety of foreign domains on a daily basis. This behavior is incredibly annoying, obviously a change from the behavior in previous versions of Windows, and definitely a detriment to productivity. I hope there's a way to get around this issue that I simply haven't come across yet...Thanks for reading!

Hi, This issue occurs because of a design change in Windows Vista. To resolve this issue, you must use the Fully Qualified Domain Name (FQDN) of the local resource to access it. For more information, please refer to the following Microsoft Knowledge Base: When you try to access a local resource over a VPN connection, you are always prompted for authentication in Windows Vista http://support.microsoft.com/kb/948067 Hope it helps.