I'm using Ganeti and encountered a problem  with migrating KVM virtual machines. I have confirmed that this is not a problem specific to Ganeti and is also happening to the Libvirt project .
When migrating from host A to host B, everything goes fine however the guest VM (running CentOS 5.4) clock changes to approximately 600 seconds in the future. When attempting to migrate back to host B, the VM locks up and stops responding. However, if you fix the clock prior to syncing back to host A, the migration happens however the clock on the VM literally stops so the guest is pretty unusable.
I tried the same scenario using Ubuntu 9.10 for the guest OS and has different issues. Upon migrating to host B, the clock on the guest VM was ahead by over 3 days into the future. Then when I migrate it back to host A the VM locks up hard.
I can confirm I have no problem using migration when using 0.11.1.
Here's the detail information about our setup:
Hardware: Intel(R) Xeon(R) CPU 5160 @ 3.00GHz
Linux OS: Gentoo Hardened
If you need more information, please let me know and I'll be happy to provide it.