How to fix the Runtime Code 400 Form already displayed; can't show modally

Symptoms of Code 400 - Form already displayed; can't show modally

Runtime errors happen without warning. The error message can come up the screen anytime Windows is run. In fact, the error message or some other dialogue box can come up again and again if not addressed early on.

There may be instances of files deletion or new files appearing. Though this symptom is largely due to virus infection, it can be attributed as a symptom for runtime error, as virus infection is one of the causes for runtime error. User may also experience a sudden drop in internet connection speed, yet again, this is not always the case.

(For illustrative purposes only)

Causes of Form already displayed; can't show modally - Code 400

During software design, programmers code anticipating the occurrence of errors. However, there are no perfect designs, as errors can be expected even with the best program design. Glitches can happen during runtime if a certain error is not experienced and addressed during design and testing.

Runtime errors are generally caused by incompatible programs running at the same time. It may also occur because of memory problem, a bad graphics driver or virus infection. Whatever the case may be, the problem must be resolved immediately to avoid further problems. Here are ways to remedy the error.

Repair Methods

Runtime errors may be annoying and persistent, but it is not totally hopeless, repairs are available. Here are ways to do it.

If a repair method works for you, please click the upvote button to the left of the answer, this will let other users know which repair method is currently working the best.

Please note: Neither ErrorVault.com nor it's writers claim responsibility for the results of the actions taken from employing any of the repair methods listed on this page - you complete these steps at your own risk.

Method 1 - Close Conflicting Programs

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When you get a runtime error, keep in mind that it is happening due to programs that are conflicting with each other. The first thing you can do to resolve the problem is to stop these conflicting programs.

• Open Task Manager by clicking Ctrl-Alt-Del at the same time. This will let you see the list of programs currently running.
• Go to the Processes tab and stop the programs one by one by highlighting each program and clicking the End Process buttom.
• You will need to observe if the error message will reoccur each time you stop a process.
• Once you get to identify which program is causing the error, you may go ahead with the next troubleshooting step, reinstalling the application.

Method 2 - Update / Reinstall Conflicting Programs

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Using Control Panel

• For Windows 7, click the Start Button, then click Control panel, then Uninstall a program
• For Windows 8, click the Start Button, then scroll down and click More Settings, then click Control panel > Uninstall a program.
• For Windows 10, just type Control Panel on the search box and click the result, then click Uninstall a program
• Once inside Programs and Features, click the problem program and click Update or Uninstall.
• If you chose to update, then you will just need to follow the prompt to complete the process, however if you chose to Uninstall, you will follow the prompt to uninstall and then re-download or use the application's installation disk to reinstall the program.

Using Other Methods

• For Windows 7, you may find the list of all installed programs when you click Start and scroll your mouse over the list that appear on the tab. You may see on that list utility for uninstalling the program. You may go ahead and uninstall using utilities available in this tab.
• For Windows 10, you may click Start, then Settings, then choose Apps.
• Scroll down to see the list of Apps and features installed in your computer.
• Click the Program which is causing the runtime error, then you may choose to uninstall or click Advanced options to reset the application.

Method 3 - Update your Virus protection program or download and install the latest Windows Update

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Virus infection causing runtime error on your computer must immediately be prevented, quarantined or deleted. Make sure you update your virus program and run a thorough scan of the computer or, run Windows update so you can get the latest virus definition and fix.

Method 4 - Re-install Runtime Libraries

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You might be getting the error because of an update, like the MS Visual C++ package which might not be installed properly or completely. What you can do then is to uninstall the current package and install a fresh copy.

• Uninstall the package by going to Programs and Features, find and highlight the Microsoft Visual C++ Redistributable Package.
• Click Uninstall on top of the list, and when it is done, reboot your computer.
• Download the latest redistributable package from Microsoft then install it.

Method 5 - Run Disk Cleanup

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You might also be experiencing runtime error because of a very low free space on your computer.

• You should consider backing up your files and freeing up space on your hard drive
• You can also clear your cache and reboot your computer
• You can also run Disk Cleanup, open your explorer window and right click your main directory (this is usually C: )
• Click Properties and then click Disk Cleanup

Method 6 - Reinstall Your Graphics Driver

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If the error is related to a bad graphics driver, then you may do the following:

• Open your Device Manager, locate the graphics driver
• Right click the video card driver then click uninstall, then restart your computer

Method 7 - IE related Runtime Error

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If the error you are getting is related to the Internet Explorer, you may do the following:

1. Reset your browser.
• For Windows 7, you may click Start, go to Control Panel, then click Internet Options on the left side. Then you can click Advanced tab then click the Reset button.
• For Windows 8 and 10, you may click search and type Internet Options, then go to Advanced tab and click Reset.
2. Disable script debugging and error notifications.
• On the same Internet Options window, you may go to Advanced tab and look for Disable script debugging
• Put a check mark on the radio button
• At the same time, uncheck the "Display a Notification about every Script Error" item and then click Apply and OK, then reboot your computer.

If these quick fixes do not work, you can always backup files and run repair reinstall on your computer. However, you can do that later when the solutions listed here did not do the job.

Other languages:

Wie beheben Fehler 400 (Formular bereits angezeigt; kann nicht modal anzeigen) - Sie können die Show-Methode nicht verwenden, um ein Formular als modales anzuzeigen, das bereits sichtbar ist.
Come fissare Errore 400 (Modulo già visualizzato; non può essere mostrato in modo modale) - Non è possibile utilizzare il metodo Show per visualizzare un modulo come modale già visibile.
Hoe maak je Fout 400 (Formulier al weergegeven; kan niet modaal worden weergegeven) - U kunt de methode Tonen niet gebruiken om een ​​formulier als modaal weer te geven dat al zichtbaar is.
Comment réparer Erreur 400 (Formulaire déjà affiché ; ne peut pas afficher modalement) - Vous ne pouvez pas utiliser la méthode Show pour afficher un formulaire en tant que modal qui est déjà visible.
어떻게 고치는 지 오류 400 (양식이 이미 표시되었습니다. 모달로 표시할 수 없습니다) - Show 메서드를 사용하여 이미 표시되는 모달로 양식을 표시할 수 없습니다.
Como corrigir o Erro 400 (Formulário já exibido; não pode mostrar modalmente) - Você não pode usar o método Show para exibir um formulário como modal que já esteja visível.
Hur man åtgärdar Fel 400 (Formulär visas redan; kan inte visa modalt) - Du kan inte använda metoden Visa för att visa ett formulär som modalt som redan är synligt.
Как исправить Ошибка 400 (Форма уже отображается; не может отображаться модально) - Вы не можете использовать метод Show для отображения формы как модальной, которая уже видна.
Jak naprawić Błąd 400 (Formularz już wyświetlony; nie można pokazać modalnie) - Nie można użyć metody Show, aby wyświetlić formularz jako modalny, który jest już widoczny.
Cómo arreglar Error 400 (Formulario ya mostrado; no se puede mostrar modalmente) - No puede utilizar el método Show para mostrar un formulario como modal que ya está visible.

About The Author: Phil Hart has been a Microsoft Community Contributor since 2010. With a current point score over 100,000, they've contributed more than 3000 answers in the Microsoft Support forums and have created almost 200 new help articles in the Technet Wiki.

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