Converter Windows Server Core 2008r2 for VMware ESXI 5.5

Hello,

I need convert a machine Windows Server Core 2008R2 for VMware ESXI 5.5. I use VMWare vCenter Converter Standalone client 5.5, but when try convert this machine the following error message:

FAILED: Unable to create a VSS snapshot of the source volume(s). Error code:127 (0x0000007F).

Someone can help me?

Thanks!