Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Ova tema je arhivirana. Pitajte drugo pitanje ako vam je potrebna pomoć.

C:\PROGRA~1\MOZILL~1\xul.dll Access is denied.

FPA
FPA
more options

Hi, I'm getting the following error messages when using Firefox:

Microsoft (R) Visual C# Compiler version 4.8.3752.0 for C# 5 Copyright (C) Microsoft Corporation. All rights reserved.

This compiler is provided as part of the Microsoft (R) .NET Framework, but only supports language versions up to C# 5, which is no longer the latest version. For compilers that support newer versions of the C# programming language, see http://go.microsoft.com/fwlink/?LinkID=533240

C:\PROGRA~1\MOZILL~1\xul.dll Access is denied.

Visual C# Compiler latest version is 4.8.3752.0. So I'm scratching my head to understand what's going wrong?

Please advise

Can someone let me know

Hi, I'm getting the following error messages when using Firefox: Microsoft (R) Visual C# Compiler version 4.8.3752.0 for C# 5 Copyright (C) Microsoft Corporation. All rights reserved. This compiler is provided as part of the Microsoft (R) .NET Framework, but only supports language versions up to C# 5, which is no longer the latest version. For compilers that support newer versions of the C# programming language, see http://go.microsoft.com/fwlink/?LinkID=533240 C:\PROGRA~1\MOZILL~1\xul.dll Access is denied. Visual C# Compiler latest version is 4.8.3752.0. So I'm scratching my head to understand what's going wrong? Please advise Can someone let me know

All Replies (2)

jscher2000 - Support Volunteer
jscher2000 - Support Volunteer
  • Top 10 Contributor
more options

Hi FPA, please ignore the fake support email address someone is spamming here. A genuine community support volunteer will reply in this thread. https://support.mozilla.org/questions/1289064

jscher2000 - Support Volunteer
jscher2000 - Support Volunteer
  • Top 10 Contributor
more options

Could you describe the circumstances of the message in a little more detail? Is that a popup you can dismiss and then everything is normal, or does it prevent you from running Firefox?

If Firefox won't run, we usually suggest:

Clean Re-install

This takes about 5 minutes. It's not about your settings, it's about making sure the program files are clean (no inconsistent or alien code files). As described below, this process does not disturb your existing settings. It's not essential to uninstall Firefox, but you can if you like, saying No to any request about removing personal data.

If you want to make a backup first just in case, see: Back up and restore information in Firefox profiles

(A) Download a fresh installer for Firefox to a convenient location:

https://www.mozilla.org/firefox/all/

(B) Exit out of Firefox (if applicable).

If you have Microsoft Office installed locally, please change your default browser to Internet Explorer temporarily before the next step.

(C) Using File Explorer (hold down the Windows key and press E to launch it), right-click > rename the program folder as follows (you might have one or both):

C:\Program Files (x86)\Mozilla Firefox =to=> C:\Program Files (x86)\OldFirefox

C:\Program Files\Mozilla Firefox =to=> C:\Program Files\OldFirefox

(D) Run the installer you downloaded in step (A). It should automatically connect to your existing settings.

Any improvement at your next startup?