Microsoft Azure Backup does not work

I use Windows 7 and implement step by step the following guide:

http://azure.microsoft.com/blog/2014/11/04/back-up-your-data-to-the-cloud-with-3-simple-steps/

I see my PC in "Recovery Services -> my recovery service -> servers" on Azure Portal

But when I try to use copy my data to Azure using Microsoft Azure Backup I get an error:

NameMessageF:\Microsoft Azure Recovery Services Agent was unable to create a snapshot of the selected volume. Please try the operation again. If the issue persists, contact Microsoft Support. (0x186C2)

it happens after long waiting "Backup progress"

I tried different folders etc. No result. The same error.