Do not use use the "Scripted Install" task, use the execute file task and call the setup.exe from a server share. In the command line put your unattend info and that should get you past your problem right now. that is what I had to do, but I have since put that on the back burner and decided that an image of vista (Since it doesn't get all bent out of shape about the HAL) is the best idea. You can use the waik tools and inject drivers as new hardware drivers is required and you can inject different unattended xml's as needed during the provisioning task.
Hopefully LANDesk will be able to resolve the issue with the scripted install not working for vista, but until then we get to monkey our way around the issues.