On Windows Vista when you map a drive under your admin account you will find that your mapped drive is not available after you switch to your full token via a RunAs or Consent dialog. This is by design because there are actually two tokens in play here. What happens is the LSA recognized that you are admin at logon and creates two logons. The first with a "filtered" token or non-admin which is used to render your desktop and the other containing your full token to be available after consent dialogs.
If you set the following key it will change how SMB shares are mapped.
EnableLinkedConnections = 1 (DWord)