Challenge
In the log file you see that IP-address is returned in IPv6 style:
Cannot connect to host [fe80::69cc:xxxx:xxxx:xxxx%17] over VIX library. Login: [xxxxx]. GuestLogin: [xxxxx].
Error while connecting to the host: [fe80::69cc:xxxx:xxxx:xxxx%17].
VIX Error: Failed to resolve host Code: 30006
Freezing guest operating system
Veeam Guest Agent is not started
Veeam Backup and Replication does not support IPv6 protocol for VSS related procedures.
Solution
Disabling IPv6 on the guest OS helps to resolve the issue. You can find the article with the exact instructions on how to do that on a Microsoft Knowledge Base site:
http://support.microsoft.com/kb/929852