Well we haven't seen the issue return at all since we changed the System Profile from "Performance per Watt" to "Performance".  I would start there first.  It's been three months and none of our T320's do this anymore.  We're 90% sure this is the solution.
Twice now I have had the Exchange 2010 guest on my W2K8 Standard Server with Hyper-V suddenly suffer a massive amount of latency and become practically locked up out of the blue.  After hours of troubleshooting, rebooting, and researching - as a last-ditch effort I noticed that the BIOS was out of date.  I upgrade BIOS and then everything magically works again. Anywhere from 2-4 months pass and rinse & repeat.  I'm going out on a limb here but I suspect that there's something about the system that gets flushed out during a bios update that is causing the problem, but I'm at a loss to determine what that is.  I want to proactively avoid having my customer's Exchange server fail, but it goes against my better judgment to apply BIOS updates proactively.  We've had the motherboard swapped out already due to a bad DRAC, and the problem keeps happening. I could use some help in identifying what else I can do to prevent this from happening in the future.  TIA
PE T320 Hyper-V Guest latency fixed by BIOS update to Host