We're getting a similar issue trying to install AutoCAD 2007 network licensing, single server. The difference here is: the error happens outside the subnet of the licensing server. The 1619 error is rarely thrown when the workstation/client is in the same subnet as the licensing server.
Like you, we've drilled through the permissions and share setup 15 times. Everything's Full Control, at every level, including the share. Even added NT 4.0 compatibility & that the executable can be run by non-admin users. This share is dangerously wide-open, and yet without success 85% of the time.
AutoCAD 2006 was a pain, but there's something really not right with the deploy MSI for AutoCAD 2007.
Daniel Bridgman
Smith College