• New: VCB file-level mount of Windows Server 2008 using NBD transport mode fails with an Disk library failed (NBD_ERR_GENERIC) error
  

  When the disk.EnableUUID parameter in the virtual machine settings is set to True on a Windows Server 2008 virtual machine, the VCB file-level mount using NBD transport mode will either fail with a Disk library failed (NBD_ERR_GENERIC)error or might stop responding, and the vcbMounter command does not run.

  Workaround: Set the disk.EnableUUID parameter in the virtual machine settings to False by performing the following steps:

  a) Power off the Windows Server 2008 virtual machine through vSphere Client.
  b) Click Settings > Options >General > Configuration Parameters.
  c) Set disk.EnableUUID to False.
  d) Save the settings.
  e) Power on the virtual machine.

Rif: http://www.vmware.com/support/vsphere4/doc/vsp_vcb_15_u2_rel_notes.html