KB2710870–No DHCPv4 Address After Restarting Hyper-V VM with Vista, Win7, W2008 or W2008 R2

Microsoft has posted a support article that deals with a situation where a DHCPv4 IP address cannot be obtained after you restart a Hyper-V virtual machine that is running Windows Vista, Windows 7, Windows Server 2008 or Windows Server 2008 R2.

The description is:

The time zone on the virtual machine is set to a time zone other than Pacific Standard Time (PST). In this situation, you may experience a DHCP IP address acquisition issue in the following scenarios:

• The guest operating system and the host operating system are set to use the same time zone other than PST, such as Eastern Standard Time (EST). The Hyper-V time synchronization service is enabled. In this situation, the DHCPv4 IP address cannot be obtained after you restart the guest operating system for the first time.
  Note This issue only occurs after you restart the virtual machine for the first time.
• The guest operating system and the host operating system are set to use different time zones. For example, the guest operating system uses the PST time zone, and the host operating system uses the EST time zone. The Hyper-V time synchronization service is enabled. In this scenario, the DHCPv4 IP address cannot be obtained after you restart the guest operating system.
  Note This issue occurs every time that you restart the virtual machine.

A hotfix is available from Microsoft to fix the issue.