Hi,  I upgraded our VMM 2008 R2 SP1 environment to VMM 2012 SP1 RU2 last month which includes a couple of clusters and several standalone hosts.

Since then the VMM agent on the hosts is crashing regularly, every 1-3 hours for some hosts.

I've attached a log from event viewer showing the vmmagent.exe crashing below.

The Hyper-V hosts are all WS2008 R2 SP1.
VMM Server is WS2012
VMM is 2012 SP1 RU2

I've looked at the Hyper-V hosts and VMM server app and system event logs and there is nothing in there of significance.

One thing that seems consistent is the more load the Hyper-V server is under the most frequently the VMMAGENT will crash.

To help alleviate this issue I have set the vmmagent service to always restart after crashing although this doesn;t help when trying to P2V etc as the job fails when the host agent crashes.

Have you opened a case at MSFT Support? 

Are you running Windows Management Framework 3? 

if you have SCCM 2012 in your environment, and if the SCCM 2012 agent installed on hyper-v host.

SCCM cause this:

http://social.technet.microsoft.com/Forums/en-US/virtualmachingmgrsetup/thread/77f94d42-91a0-4fe2-8ae0-e631e4fa5159

If needs be, we will create a case with Msft.

The hosts are not running WMF3.

After removing the Op's Mgr 2012 and Config Mgr 2012 agents from the hosts the VMM agent stops crashing.

A WMI issues?

It's know issue for sccm 2012 sp1 client with vmm 2012 without sp1

My VMM is fully up to date- VMM 20121 SP1 RU2