Introduction
I’ve run into this issue whenever setting up Microsoft DaRT 8.1 on Windows Server, and therefore assume that this is a common problem.
Microsoft DaRT 8.1 is intended to run on Windows Server 2012 R2 but installs fine on Windows Server 2012 RTM. This is as long as you run the setup file as an administrator install:
msiexec /a MSDaRT81.msi
Refer to Johan Arwidmark’s excellent blog post about setting up DaRT 8.1 together with MDT monitoring: http://www.deploymentresearch.com/Research/tabid/62/EntryId/131/Adding-DaRT-8-1-from-MDOP-2013-R2-to-ConfigMgr-2012-R2.aspx.
The issue I ran in to was when running DaRT Remote Control on the client from MDT Monitoring:
“MMC has detected an error in a snap-in and will unload it.”

After pressing “OK”, I saw these two error messages:
“Object reference not set to an instance of an object.”

“This snap-in performed a non-valid operation and has been unloaded. To continue working with this snap-in, restart MMC or try loading the snap-in again.
Exception Type: System.NullReferenceException
Exception Message: Object reference not set to an instance of an object.
at. Microsoft.BDD.Workbench.MonitoringGeneral.buttonDaRT_Click(Object sender,EventArgs e)

How to troubleshoot the MMC snap-in error
To troubleshoot this behavior, I opened Process Monitor to see what happened when I pressed the “DaRT Remote Control” button. Download Process Monitor from here:
http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx
I could see that DaRT (mmc.exe) was trying to access a registry key: “HKLM\SOFTWARE\Microsoft\DaRT”

Looking in the registry, I could see that there was no key with this name there.
How to fix the error
The solution was to create a string value called “InstallPath” which pointed to the installation path of DaRT.
The string value should be in HKLM:\SOFTWARE\Microsoft\DaRT\v8.1

After making the registry change, I just started a new DaRT Remote Control session, and it worked perfectly 🙂
Conclusion
I have just described how to solve one MMC error related to Microsoft Dart. Fortunately, many new Microsoft products have moved away from MMC.
Please drop a comment if you know why this error occurs and if I am doing it wrong in any way 🙂
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