What is this?

Hi JB2_380

Welcome to Microsoft Community.

Based on your description, I understand that you receive a random message before logging in again, and I know exactly how you feel!

From the fact that you provided this specific message, at this point it indicates that the .NET assembly file “System.Collections.Concurrent.ni.dll” is corrupt.

There could be several reasons for this:

1. The .NET Framework is corrupt, which prevents it from loading properly.
2. The version of .NET Framework you are using may not be compatible with your application or operating system.
3. Malware can sometimes target system files and cause errors.
4. your application may depend on other components that are missing or not properly installed.

If it does not affect your normal use, it is generally not a particularly significant problem.

However, here are some suggestions to help you resolve the problem. However, this first reply may not be able to solve your problem due to the lack of information and the fact that it requires different aspects of troubleshooting, so please understand and provide more information (pictures would be great!) in your reply. Thank you very much!

Option 1: Try to re-register the DLL from the command line.

Click “Windows Logo Key” to open the search bar -> Enter “cmd” in the search bar and open it with administrator privileges -> Please enter the following command

regsvr32 System.Collections.Concurrent.ni.dll

Please note: This method may not work depending on the version of.

Option 2: We try to reinstall the uninstallation and then reinstall the appropriate version of the .NET Framework for your application.

Option 3: If this error is related to a specific application, uninstall the application and reinstall it using the original installation media.

Because generally this error is caused by some application calling this dll.

Option 4: Please try to clean boot your computer.

Since clean boot only uses a limited set of files and drivers, it can help us to effectively troubleshoot the possibility of problems caused by third-party applications, driver conflicts, and so on.

You can refer to Clean Boot for more information: How to perform a clean boot in Windows - Microsoft Support

After clean boot, please slide down the webpage after opening the link and find “How to determine what is causing the problem after you do a clean boot” This is a dichotomy that can help us pinpoint the service that is causing the problem and disable it!

Disclaimer: A “clean boot” starts Windows with a minimal set of drivers and startup programs. It helps to determine whether a background service is interfering with your game or program and to isolate the cause of a problem. These steps of "clean boot" might look complicated at first glance. However, to avoid any trouble for you, please follow them in order and step-by step so that it will help you get back on track.

In general, however, if this error does not affect your normal use and you find it troublesome to troubleshoot the error, you can also leave these actions in place for the time being.

If you find the application that is calling the dll file, you can also let me know in a reply and there may be a specific way to fix the problem.

I sincerely hope that the above solution will solve your problem. Please feel free to contact me if you have any problems or still can't solve them. (Photos related to the question would be great!) .

I looking forward to hearing back from you. 

Best Regards

Arthur Sheng | Microsoft Community Support Specialist