It is a known issue in Virtual Machine Manager 2008 R2 that if you select 3 Virtual CPU (Processors) for a Virtual Machine in Hyper-v, the VMM Administrator Console will crash and terminate immediately when you try to view the properties of that Virtual Machine.
The workaround is to only select 1, 2, or 4 virtual CPUs for your VMs and that is the only supported configuration by VMM today. In the VMM console, you can only select the same 3 options.
If you get in a situation like this where the console is crashing, change the vCPUs from Hyper-V Manager, and call the refresh-vm cmdlet in VMM to update the "offending" VMs. Once you do that, you will be able to restart the VMM Administrator Console without crashing.
To identify the number of vCPUs on each VM, use this cmdlet.
get-vm | select name, hostname, CPUCount