How to Fix Runtime Error 91

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A runtime error is basically an error that occurs during a programs “runtime”, to put it simply. Each runtime error has its own error code, such as 91, in this case. When an individual experiences a runtime error 91 on their computer, it’s usually accompanied by a “Object variable set to nothing” error message.

Runtime error 91 is a fairly common error on Windows based systems that usually occur at random moments. This error doesn’t have a clear defined cause; however, the Visual Basic DCOMCnfg.exe on your computer is one known culprit for this error; which is usually the result of damage, and/or corruption to this file. With that said, there are a number of things that you can do, when you find yourself in this situation.

Symptoms of Runtime Error 91

There are a number of symptoms individuals may experience when they encounter an error 91, but of the various symptoms, the most common are the following:

  • The active program window crashes, just as the Error 91 dialog box appears.
  • Error 91 frequently crashes, as you attempt to run the same application.
  • “Object variable or with block variable not set” error message is displayed.
  • Windows performance becomes very slow and unresponsive to both keyboard and mouse input.
  • Computer randomly freezes for several seconds at a time.

The runtime error 91 can occur while you are installing an application, while you are using a program, within a Windows based environment, during the startup phase of your computer or while it is shutting down, or even when installing Windows for the first time. Keeping note of when you actually experience this error is very important, as it will help you when troubleshooting the problem.

Cause of Error

Already speaking briefly about the cause of this error, .NET Framework and Visual Studio (in addition to DCOMCnfg.exe) are also known to be related to this error; these are tools used in the development of applications.

Within a programming environment, the runtime error 91 would tell the programmer that an invalid variable, which has the value of “nothing”, is being referenced to.

Usually, it’s not known whether or not an application will generate a runtime error 91, till after the user attempts to run it. Error 91 can also be caused by a network blackout, while an application is attempting to download additional data from its server.

The general consensus amongst this error is that it occurs, when attempting to use an application that has issues with the variables within it.

A variable is essentially a container that a programmer will use to store flexible data. An invalid variable could relate to the wrong kind of data being stored in a variable, or the variable being incorrectly referenced.

Fixing this error will thus, entail repairing the coding of a particular application, in order to prevent the error from reappearing, every time you try to use it.

Fixing Runtime Error 91

Below are a number of fixes that an individual can attempt when trying to fix this problem. This error is a pretty difficult one to fix, because of the personal nature of it, as it relates to the application. However, there are still many things that you can do, to at least mask the problem.

Use Registry Cleaner

One thing you should definitely do before anything else is use a registry cleaner to scan through your system so that it can repair any damaged configurations which could be aiding the runtime error.

The function of the registry cleaner is to fix errors within your computers registry, the registry is the area of the computer were all you’re most important data is stored, such as system options, preferences and various other things.

Whenever you install and use an application on your computer, numerous registry settings are created and used, but this process can also lead to redundant entries, invalid registry keys and damaged settings.

Fixing this problem will require you to use a registry cleaner, which will scan through your entire system, locate all of these errors and fix them. With that said, there are various registry cleaners out there, but the one I personally recommend is SpeedyPC Pro, and that’s because of its multifaceted nature. Anyway, you can pick this tool up here:


Check for Viruses

The next step you should consider doing when attempting to fix a runtime error 91, is to use an antivirus scanner. In a lot of situations, this issue is the result of malware or viruses running within the background of the computer causing the application to crash, every time you use it. Because viruses spread, infecting more components of your operating system over time, it’s very important that you address it as soon as possible.

A good antivirus program should have little difficulty finding the virus on your computer, and removing it. Antivirus tools are very easy to use, the only thing that is required on your end, is to ensure that everything on it is up-to-date, especially its virus definitions.

With that said, simply run a full scan of your system, for this task. If you don’t have an antivirus tool on your computer, or you think your tool isn’t very good, then I recommend you use SpyHunter, alternatively you could check out my post on the very best antivirus tools.

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The solution(s) below are for ADVANCED level computer users. If you are a beginner to intermediate computer user, I highly recommend you use the automated tool(s) above!

Reinstall Application

If all other methods have failed, then you should consider reinstalling the application. There is a good chance that the error was due to an incomplete installation, in which case, a reinstallation should fix it.

When it comes to reinstalling the application, you want to ensure that every trace of the application is removed; this includes redundant files, folders and registry entries, before you reinstall it.

However, in order for you to do this, you will need to use the uninstallation tool called Perfect Uninstaller. This powerful removal tool is capable of not only removing applications using the conventional InstallShield, but also running independent scans of your operating system and registry and removing all associated data. Anyway, you can acquire this excellent tool from here:


Check for Patches

Whenever an individual encounters a runtime error 91 while attempting to run a program, there is very little they can do about the coding for that particular program. However, one possibility entails checking the website of the developer, to see whether or not they have released a patch that fixes the bug in the code.

If you do find a patch, simply download it, and apply it to the program. The patch should come with its own update facility to make the update process more seamless.

Alternatively, if the program has its own update utility, you can try that, before heading off to the website of the developer.

Check Windows Updates

Another idea that has proven to be quite effective at fixing this problem involves checking for Windows updates. This is because, not only do developers release patches for bugs in their programs, but so does Microsoft, for their operating system.

If the application that is generating a runtime error 91 came preinstalled with your computer, when you purchased it, then you can try checking the websites of the computer manufacturers for any updates for this problem.

This is an excellent way for you to find all the appropriate updates for your computer make and model. You may find updates that fix the runtime error in additional to updates that may improve the overall performance of your computer. By keeping your computer up-to-date with the latest updates, not only will it secure it from bugs, but it will also secure it from hacks and viruses.

Configure DCOMCnfg.exe

If the runtime error you’re experiencing is due to the DCOMCnfg.exe, then you will need to reconfigure its settings to fix the problem. The purpose of this program is to control file permissions and various other things, related to Visual Basic, on your computer.

Unfortunately, if the necessary steps are not taken to rectify this problem, the error will persist, thus it’s important that you configure DCOMCnfg.exe to Allow “Everyone”.

If you don’t know how to do this, I suggest you check out the following report:

Turn Off Error Messages

If you’ve searched for a fix for the application, but were unable to find anything, then the first thing you should do is contact the developer to notify them about the problem.

The next option available to you is to turn off script debugging, that way, you won’t have to see the error message, every time it occurs. After all, the error message is of little value to you.

The Machine Debug Manager is the tool that operates the script debugging, a tool that you can control through Internet Explorer. Anyway, to disable it, simple do the following:

1. First, ensure you have booted into your computer with administrative rights.

2. Then, double click on the Internet Explorer Icon, to start the browser.

Click on IE Icon

3. Once Internet Explorer starts, click on Tools [Cog] -> Internet Options.

Tools -> Internet Options

4. This will bring up the Internet Options, from here, click on the Advanced Tab, and check the box next to Disable Script Debugging (Internet Explorer) and Disable Script Debugging (Other) then click on OK.

Check both Script Debugging Boxes

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