I agree: do not reset your computer.

When you get the endless loading icon, could you check the address bar for any notification icons? These typically appear to the left of the URL and may indicate that a plugin needs to be activated, or that there is a security problem with the page. Click the icon for more information.

And the usual: When you have a problem with a site that previously worked normally, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Bypass Firefox's Cache

Use Ctrl+Shift+r to reload the page fresh from the server.

Alternately, you also can clear Firefox's cache completely using:

orange Firefox button (or Tools menu) > Options > Advanced

On the Network mini-tab > Cached Web Content : "Clear Now"

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site:

• right-click and choose View Page Info > Security > "View Cookies"
• Alt+t (open the classic Tools menu) > Page Info > Security > "View Cookies"

In the dialog that opens you can remove the site's cookies individually.

Then try reloading the page. Does that help?

Thank you so much for your fast response. Some of what you recommended, I'd already tried. However, I started at the top of your suggestion and worked my way down. Nothing worked. (And there weren't any notification icons in the address bar, either.)

I'm just stumped as to what could be the difference between Firefox on this computer and on the old computer. I don't know if it makes any difference, but the OS on the old computer is Win7 Home x64 and on this computer it's Win7 Pro x64.

As a test to work around your current settings and see how Firefox runs "uncustomized" on your system, could you do a two-minute experiment?

Create a new Firefox profile

A new profile will have your system-installed plugins (e.g., Flash) and extensions (e.g., security suite toolbars), but no themes, other extensions, or other customizations. It also should have completely fresh settings databases and a fresh cache folder.

Exit Firefox and start up in the Profile Manager using Start > search box (or Run):

firefox.exe -P

Don't delete anything here Any time you want to switch profiles, exit Firefox and return to this dialog.

Click the Create Profile button, choose a name like July22, and ignore the to option to choose a folder location. Then start Firefox in the new profile you created.

Do the two problem sites work any differently in the new profile?

When returning to the Profile Manager, you might be tempted to use the Delete Profile button. But... it's a bit too easy to accidentally delete your "real" profile, so I recommend resisting the temptation. If you do want to clean up later, I suggest making a backup of all your profiles first in case something were to go wrong.

Thank you for hanging in there with me.

I created a new profile and both sites worked correctly in the new profile. I checked and all the "plugins" were the same for both. Then I went back to the default profile and disabled ALL "extensions" and restarted FF.

The problem still exists.

Can you recall customizing how Firefox handles cookies? You could check the privacy settings; this article describes the most broadly compatible settings: Websites say cookies are blocked - Unblock them.

Thank you.

I checked cookie options and here are the current settings:

 ~ Accept cookies from site, no exceptions.
 ~ Accept third-party cookies.
 ~ Keep until they expired

I tried specifically allowing cookies for both GoodReads and GetResponse, and they still don't load properly.

Maybe it would be easier to move your most important data into the new profile instead of trying to find the needle in the haystack in the old profile?

To start, I would copy the places.sqlite (bookmarks + history) database from the old profile to the new profile. If you use Firefox to save passwords, you can copy those files over, too. Then test whether the sites still work normally in the new profile. If so, you could install your most important extensions and test again.

This article describes the key settings files: Recovering important data from an old profile.

Please make sure Firefox is closed when copying/replacing settings files.

Before beginning the operation, you might want to make a backup of your current profile contents. You can open your current Firefox profile folder using either:

• "3-bar" menu button > "?" button > Troubleshooting Information
• Help menu > Troubleshooting Information

In the first table on the page, click the "Show Folder" button

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• File menu > Exit

Pause while Firefox finishes its cleanup, then copy everything to a safe location (e.g., external drive, or a folder you create under Documents).

Or... you could try the Reset feature. This article describes what data is retains when automatically setting up your new profile, and what is lost: Refresh Firefox - reset add-ons and settings.

I was coming to the same conclusion. Perhaps there is something in the profile data that is OS specific. Even though one would expect that shouldn't happen going from Win7 Home to Win7 Pro.

I'm afraid I can't spend any more time on this today, but I'll come back and let you know if that takes care of the problem. Maybe I'll even be able to pinpoint what caused the issue. If so, I'll let you know for future reference.

Thank you so much for your generous time. I definitely appreciate it.