At that time, can Firefox connect to non-secure addresses such as

http://example.com

If you are using a network access point that requires a sign-in (such as some wi-fi networks), you may need to do that using a non-secure address before you can access secure addresses.

Otherwise, is it possible that an intermediary program is intercepting your browsing? Programs that do that include Avast, AVG, Bitdefender, ESET, Kaspersky, and Microsoft Family Safety. I don't know why Firefox would trust fake certificates generated by these programs before sleep/wake and stop trusting them afterwards. ??

Oh, you also could check whether Firefox switched to offline mode. This is available here:

• "3-bar" menu button > Web Developer > Work Offline
• (menu bar) File > Work Offline

If there's a checkmark, click it to "uncheck" that option.

There are other things that need attention.

The System Details list shows that you have an outdated Flash plugin, current is 32.0.0.156 (32.0 r0).

• Shockwave Flash 28.0 r0

You can find the installation path of a plugin on the about:plugins page.

You can download the latest NPAPI Flash plugin for Firefox on this page.

• https://get.adobe.com/flashplayer/otherversions/

Make sure to remove checkmarks for including unwanted additional software.

You can check the connection settings.

• Options/Preferences -> General -> Network: Connection -> Settings

If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.

See "Firefox connection settings":

• https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can