The Windows Server Backup on Windows 2008 (equivalent to NTBackup on Windows 2003) is no longer Exchange-aware, meaning if you were planning to use Volume Shadow Copy and this server backup tool, then you have to wait for Microsoft to release a VSS plugin who knows when… terrible…

Here are bunch of people complaining about this limitation – http://social.technet.microsoft.com/forums/en-US/exchangesvrgeneral/thread/14b80759-5938-46ed-846b-c698cda36327/#page:3