Microsoft Deployment Workbench MMC Has Detected an Error in a Snap-in and Will Unload it
I’ve run in to this issue every time when setting up DaRT 8.1 on Windows Server 2012 RTM, and therefore assume that this is a common problem. Please drop a comment if you know why this occurs and if I am doing it wrong in any way 🙂
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 administra install:
msiexec /a MSDaRT81.msi
Refer to Johan Arwidmark’s great 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)
In order to troubleshoot this behavior, I opened Process Monitor to see what actually happened when I pressed the “DaRT Remote Control” button. Download Process Monitor from here:
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.
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 🙂
About the author
Daniel Classon works as a Senior Consultant at Mansoft, focusing on Microsoft Configuration Manager, Windows 10 and Powershell