Hyper-V Program Manager
When I read this post that states that the VSS (Volume Shadow Copy Services) functionality in Virtual Server 2005 R2 SP1 Beta 2 did not work with NTBackup - I was worried that we might have done something wrong, but a little bit of investigation revealed that this is actually expected. It appears that NTBackup does not support backing up software that provides its own VSS support.
However, you can use the tools that are provided in VSS SDK or a full backup program with VSS support to backup Virtual Server.
SQL Server has its own VSS writer, and NTBackup backs it up just fine...