It's not a Vista thing, well it could be!!
With Vista it's absolutely important that you have set full permissions on all your folders in Poser, if you haven't you will get problems laoding content, DAZ installers seem particularly bad, they throw up an error message but they install ok if you ignore the message!
Also make sure you run Poser or any other 3D software in Admin mode, again if you don't you'll have problems!

Injustice will be avenged.
Cofiwch Dryweryn.