Also, sorry for being in a hurry and posted the wrong properties, as they are for AD user, and not for AD Terminal Server user

On the other hand, did you get a look here ? http://msdn.microsoft.com/library/en-us/termserv/tsref_2o8o.asp
seems it's only for .NET, but can you check if some properties are also working with your vbs script ? It may need to be run from the AD Terminal server