ERR_EMPTY_RESPONSE

The AdwCleaner report has been moved to: Is my Computer Infected

 

The connection problem and the adware may not be related...... it could just be a coincidence.
So for now, we'll treat it as 2 separate issues.

So is it just https sites?

 

What settings?
Did you run a full browser reset?

Using a local account (limited user) will afford you some extra security.
But you would need to leave your Admin account as it is and add the local account.
There are certain things that you can only do from an Admin account.... that's why you would still need it.

How to Create a New Local User Account in Windows 10

 

Are these the instructions you followed:

To Reset Firefox

• At the top of the Firefox window, click the Help menu and select Troubleshooting Information
• Click the Reset Firefox… button in the upper-right corner of the Troubleshooting Information page.
• To continue, click Reset Firefox in the confirmation window that opens.
• Firefox will close and be reset. When it's done, a window will list the information that was imported.
• Click Finish and Firefox will open.

Note:
After the reset is finished, your old Firefox profile information will be placed on your desktop in a folder named "Old Firefox Data." If the reset didn't fix your problem you can restore some of the information not saved by copying files to the new profile that was created.
If you don't need this folder any longer, you should delete it as it contains sensitive information.

The reset feature works by creating a new profile folder for you while saving your most important data.

Firefox will try to keep the following data:

• 
  
  
  • Bookmarks
  • Browsing history
  • Passwords
  • Cookies
  • Web form auto-fill information
  • Personal dictionary

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Reset IE back to the defaults.

• Close any Internet Explorer or Windows Explorer windows that are currently open.
• Open Internet Explorer by clicking the Start button, and then clicking Internet Explorer.
• Click the Tools button, and then click Internet Options.
• Click the Advanced tab, and then click Reset.
• Select the Delete personal settings check box if you would like to remove browsing history, search providers, Accelerators, home pages, and InPrivate Filtering data.
• In the Reset Internet Explorer Settings dialog box, click Reset.
• When Internet Explorer finishes applying default settings, click Close, and then click OK.
• Close Internet Explorer.
• Your changes will take effect the next time you open Internet Explorer.

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To reset Google Chrome

• Click the Menu option button at the top right of the Google Chrome screen
• Select Settings.
• Click Show advanced settings and find the "Reset browser settings” section.
• Click Reset browser settings.
• In the dialogue that appears, click Reset. Note: When the "Help make Google Chrome better by reporting the current settings" tick box is selected you are anonymously sending Google your Chrome settings. Reporting these settings allows us to analyse trends and work to prevent future unwanted settings changes.

Resetting your browser settings will impact the settings below:

Default search engine and saved search engines will be reset and to their original defaults.
Homepage button will be hidden and the URL that you previously set will be removed.
Default startup tabs will be cleared. The browser will show a new tab when you startup or continue where you left off if you're on a Chromebook.
New Tab page will be empty unless you have a version of Chrome with an extension that controls it. In that case your page may be preserved.
Pinned tabs will be unpinned.
Content settings will be cleared and reset to their installation defaults.
Cookies and site data will be cleared.
Extensions and themes will be disabled.

 

If you start Internet Explorer.... click Settings ( the Gear wheel, top right corner)
Select Internet Options
Select the Security tab......
What is the Security level setting?
Is it Medium - High? .... if so, that's OK.
If it's High .... knock it down to Medium - High , then click on Apply and see if there's any difference.