Error 1001. InstallUtilLib.dll: Unknown error.

This is a nice error message I received today when attempting to install one of my applications that interfaces with MSCRM 2011. My application is deployed from a MSI file which I created from Visual Studio. The installer checks prerequisites, asks a few basic CRM connection questions and then attempts to deploy the application. Halfway through deploying the application I received the error Error 1001. InstallUtilLib.dll: Unknown error.

 Whats the Cause?

The cause is simple, the .NET Runtime on the target machine was corrupt. When I first attempted to install my application the prerequisites check detected I required the .NET 4 Runtime. Halfway through the installation the machine played up and the runtime didn’t install correctly. On completion it didn’t even ask me to restart the machine! On the second install attempt the prerequisites check thought .NET was installed and so attempted to deploy my application. As .NET 4 wasn’t installed correctly the deployment failed and through Error 1001. InstallUtilLib.dll: Unknown error.

Whats the Fix?

The fix for this error is very simple.

  • Reboot the target machine if you have just attempted the .NET installation. This will clear the pending reboot.
  • Download the your current version of the .NET runtime. Rerun it and choose to fix the .NET runtime currently installed on your machine. (If you wish, you can choose to uninstall the current version of .NET and then reinstall).
  • Reboot the target machine and continue with the installation / running of your application.

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