Time drift issues are common when working with virtualization. I found a good article about Hyper-V time synchronization issues at Ben Armstrong's Blog at http://blogs.msdn.com/b/virtual_pc_guy/archive/2010/11/19/time-synchronization-in-hyper-v.aspx.
I was able to resolve the issue by installing the NTP service:
yum install ntp
The default NTP servers were OK but they can be changed with:
The following commands then started the service, synced the guest, and set the NTP service to start automatically.
service ntpd start