Try running Firefox in Diagnose Firefox issues using Troubleshoot Mode. If it functions without displaying it in that configuration, then one of your add-ons is the culprit.

I tried all the suggestions but nothing helped. Thank you.

Do you have AVG Safe Search installed, or the AVG Linkscanner? If so, disable both by clicking the orange Firefox button, go to Add-ons, then Extensions and then try and access Yahoo again.

'I don't have those items you mentioned. I have disabled all add-ons several times, thru process of elimination I found nothing changes. Back to square one.'

Could you please do the following.

1. In the location bar where you normally type in a web address, type about:config and hit Enter.
   
   
2. If you see a window which says "This might void your warranty!", click the button which says "I'll be careful, I promise" so you can continue with the next step.
   
   
3. In the filter at the top, copy/paste: extensions.logging.enabled
   
   
4. Double click it to change it from "False" to "True".
   
   
5. Close Firefox and then restart it again.
   
   
6. Click the orange Firefox button, then click Web Developer followed by Error Console.
   
   
7. Click the Clear All button and then close it.
   
   
8. Next, go to Yahoo Messenger again and do what you normally do which produces the error.
   
   
9. Repeat step 6 and then copy the contents of the Error Console into this thread please.

This is all I can copy and paste from the Error Console....wont allow me to select ALL and copy it. Error: Components.classes['@mozilla.org/extensions/manager;1'] is undefined Source File: chrome://jqs/content/overlay.js Line: 9

That error message indicates that you have an Add-on installed which is incompatible with Firefox 5.0

To resolve this issue, do the following.

1. Click the orange Firefox button, then click "Help" | "Restart with Add-ons disabled".
   
   
2. In the next menu, checkmark the top option which is "Disable all Add-ons".
   
   
3. Click the button which says "Make changes and restart."
   
   
4. Re-enable your Add-ons one by one checking each time in Yahoo Messenger until the problem recurs. Then you'll know which one it is which is causing the problem.
   
   

As a precaution, download the free version of Malwarebytes from http://www.malwarebytes.org/products/malwarebytes_free and run a full system scan to eliminate malware as the culprit.

I just tried the add-ons again and still no indication of what is wrong. The results are the same. Must be something in my computer that I can't discover thru scans and all the other ideas I have tried since June 21. Thank you.

What did the Malwarebytes scan reveal?

Nothing revealed in any scans.

Try creating a new Profile. See these articles.

• Profiles - Where Firefox stores your bookmarks, passwords and other user data
  
  
• Managing Profiles
  
  
• Recovering important data from an old profile

Do the following ONLY IF AVG is not your primary Anti-virus program. Look in C:\Program Files for anything AVG. If it is there, it may be your primary Anti-virus program and the following will remove AVG from your system.

Try downloading and running the AVG Remover tool to remove remnants of a previous AVG install that did not successfully uninstall. Choose one of the 2 items at the top of the list depending on whether your OS is 32-bit or 64-bit; chances are you are running Windows XP 32-bit:

• http://www.avg.com/us-en/utilities

Thank you but I already had done this using AVG Remover and all files are gone.

Error: Components.classes['@mozilla.org/extensions/manager;1'] is undefined Source File: chrome://jqs/content/overlay.js Line: 9

jqs is the Java Quick Starter add-on

Good point Ed, but what about the original post? Can you figure that one out too?

Tried disable of java quick start and nothing happens. Thanks again for the try.

You said earlier that you couldn't select all in the Error Console. That's correct because each report is abbreviated in the list.

But during the troubleshooting process, you have to do your part because we don't have access to your PC.

The solution to your problem may very well be contained in one of the other unique reports in the Error Console, so if you want to help us help you, please follow the steps in my instructions posted earlier (5th post from the top) and then we can examine the rest for clues.

I thank you all for the help you have given me. I will continue to search for an answer or just give up the use of the features on Yahoo Messenger that don't work. Thanks again.

You're welcome.