Hello. This sounds like a bizarre case. Never heard of this one before. But to attempt to solve the PC problem. You can give Firefox a Refresh via... paste "about:support" into the URL Browser bar. Refresh will remove add-ons (so list down those you do have installed for reinstallation) Refresh will reset preferences to default.

[https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings Refreshing Firefox] {web link} is a '''LAST RESORT ! !''' Refreshing Firefox -- easily fix most problems If you're having problems with Firefox, refreshing it can help. The refresh feature fixes many issues by restoring Firefox to its factory default state while saving your essential information like bookmarks and open tabs. Everything else, like user settings and add-ons, are removed. -------------------- Many site issues can be caused by corrupt cookies or cache. * Clear the Cache and * Remove Cookies '''Warning ! ! ''' This will log you out of sites you're logged in to. You may also lose any settings for that website. Type '''about:preferences'''<enter> in the address bar. * '''Cookies; ''' Select '''Privacy. ''' Under '''History, ''' select Firefox will '''Use Custom Settings. ''' Press the button on the right side called '''Show Cookies. ''' Use the search bar to look for the site. Note; There may be more than one entry. Remove '''All''' of them. * '''Cache; ''' Select '''Advanced > Network. ''' Across from '''Cached Web Content, ''' Press '''Clear Now. ''' If there is still a problem, '''[https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode Start Firefox in Safe Mode]''' {web link} A small dialog should appear. Click '''Start In Safe Mode''' (not Refresh). While you are in safe mode; Try disabling graphics hardware acceleration in Firefox. Since this feature was added to Firefox it has gradually improved but there are still a few glitches. You will need to restart Firefox for this to take effect so save all work first (e.g., mail you are composing, online documents you're editing, etc.,) and then perform these steps: '''In Firefox 54 and below:''' # Click the menu button [[Image:New Fx Menu]] and select ''Options'' (Windows) or ''Preferences'' (Mac, Linux). # Select the ''Advanced'' panel and the ''General'' tab. # Uncheck '''Use hardware acceleration when available'''. # Close Firefox completely and then restart Firefox to see if the problem persists. '''In Firefox 55 and above''': # Click the menu button [[Image:New Fx Menu]] and select ''Options'' (Windows) or ''Preferences'' (Mac, Linux). # Select the ''General'' panel. # Under '''Performance''', uncheck ''Use recommended performance settings''. Additional settings will be displayed. #;[[Image:Fx55Performance-disableHWA|width=500]] # Uncheck '''Use hardware acceleration when available'''. # Close Firefox completely and then restart Firefox to see if the problem persists. Did this fix your problems? Please report back to us! If the problem is resolved, you should check for updates for your graphics driver by following the steps mentioned in these Knowledge base articles: * [[Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems#w_turn-off-hardware-acceleration]] * [[Upgrade your graphics drivers to use hardware acceleration and WebGL]]

You can try to right-click the checkboxes and open the Inspector to see what element gets selected in case another element is overlaying the boxes. *https://developer.mozilla.org/en/Tools/Page_Inspector