Try the Firefox SafeMode.
A troubleshooting mode, which disables most Add-ons.
(If you're not using it, switch to the Default Theme.)

1. You can open the Firefox 4/5/6/7 SafeMode by holding the Shft key when you use the Firefox desktop or Start menu shortcut.
2. Or use the Help menu item, click on Restart with Add-ons Disabled... while Firefox is running.
   

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before using the Firefox shortcut (without the Shft key) to open it again.

If it is good in the Firefox SafeMode, your problem is probably caused by an extension, and you need to figure out which one.
http://support.mozilla.com/en-US/kb/troubleshooting+extensions+and+themes

Thank you for the suggestions. I tried SafeMode (both methods) and it did not fix the problem. Google Maps are still missing important elements.

The maps are running correctly in both IE8 and Chrome. So, bye-bye to Firefox after many years. I will probably just keep using Chrome.

Thanks again.

If images are missing then check that you aren't blocking images from some domains. See:

• http://kb.mozillazine.org/Images_or_animations_do_not_load

• Check the permissions for the domain in the current tab in Tools > Page Info > Permissions
• Check that images are enabled: Tools > Options > Content: [X] Load images automatically
• Check the exceptions in Tools > Options > Content: Load Images > Exceptions

You can also use these steps to check if images are blocked:

• Open the web page that has the images missing in a browser tab.
• Click the website favicon (How do I tell if my connection to a website is secure?) on the left end of the location bar.

• Click the "More Information" button to open the "Page Info" window with the Security tab selected (also accessible via "Tools > Page Info").
• Go to the Media tab of the "Tools > Page Info" window.

• Select the first image link and scroll down through the list with the Down arrow key.
• If an image in the list is grayed and there is a check-mark in the box "Block Images from..." then remove that mark to unblock the images from that domain.

Thank you, cor-el. The first three checked okay. However, after scrolling through all the images under More Info > Media, the last two images in the list of about 50 images were blocked. They were the Map Control icons. Unchecked them and the map is back to normal.

WhatEVER would have caused those images to become blocked? I've used Google Maps regularly (like DAILY) for several years with nary a problem. I also note that this hasn't happened in Chrome or IE8.

Gremlins? Each user has their own login, so nobody else uses my login.

Thanks again!

In Firefox 5 versions it was possible to block images (by accident) via the right-click context menu, but that context menu entry was removed to prevent.
If you have visited that site in Firefox 3.6.x and haven't visited it recently in Firefox 4 or 5 then you may have done that in a Firefox 3.6.x version in the past.