[from 10/7/08]
The most difficult bug we are dealing with in the Vista beta for DirectRT at this point is an installation issue. Vista seems to be much more serious about permissions than XP was. We are working to resolve this. The 13th release ought to be ready this week and hopefully this will be worked out asap. In the mean time, it sounds like you have done everything you can do. There was a recent update though which you may or may not be aware of--deleting the license dll file in the DirectRT folder can help in some cases--try deleting it and DirectRT will generate a fresh one when you try to restart it. In some cases, that has fixed the issue completely.