Error on install of CRM: SQLAccessGroup not found

I've been trying to install CRM 4.0 in a VM linked to SQL Server 2008 and Windows Server 2008.  Every time I try to run the install, I get an error message:

Action Microsoft.Crm.Setup.Server.GrantConfigDBDatabaseAccessAction failed. 
Windows NT user or group 'EHEALTHOZ\SQLAccessGroup' not found. Check the name again.

I've tried:
- a complete rebuild,
- tried using SQL 2005 instead of SQL 2008
- tried an unattended install to setup the SQLAccessGroup group in advance of the install

I'm using all the guidance Microsoft has published regarding SQL2008 and Windows 2008 support for CRM 4, but that hasn't helped.

From the server I'm installing CRM on, I can definitely browse the AD Users & Computers to find EHEALTHOZ\SQLAccessGroup

Any ideas on what might be at fault??

Thanks