Cannot Activate Vista 5384

Hello,

I work in a company with more than 10.000 Employees worldwide and we are
testing Vista Beta Build 5384 with VMware Workstation 5.51.
Actually we have several License Keys from Microsoft and have a prebuilt
VMware-Image that we copy and prepare for testuser.
We change the MAC-Adress of each copy as well as PC-Name and integrate Vista
into our Domain.

The Problem is that we actually can´t activate any more Vista Versions
although we have unused keys left. We get Error "Fehler beim Erwerb des
Rechtekontozertifikats. hr=0x8004FC10".

Does anyone knows this ?

--
I´m not here for private use.
It´s business why I´m here.