Do you have an add-on with the letters; trk ?

I don't think so.

I've called the big guys to help you. Good luck.

When or how does this show up? What are you doing at the time?

You can check for recently installed suspicious or unknown extensions.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Do a malware check with several malware scanning programs on the Windows computer. Please scan with all programs because each program detects different malware. All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender:
  http://windows.microsoft.com/en-us/windows/using-defender
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked
• https://support.mozilla.org/kb/troubleshoot-firefox-issues-caused-malware

It only happens when I'm in my Hotmail account. A couple of days after posting my initial question, it started doing the exact same thing in Firefox, when I'm in my Hotmail account on my laptop. The original question happened on my desktop.

I don't know whether Hotmail/Outlook uses Flash; do you see a plugin notification icon in the address when you're on the page?

I mention Flash because a common cause of unresponsive script errors on Windows 7 is the protected mode feature of the Flash player plugin. That feature has security benefits, but seems to have serious compatibility issues on some systems. There is a hidden setting to disable it; I suggest trying this for a day to see whether it helps:

(A) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(B) In the search box above the list, type or paste flash and pause while the list is filtered

(C) Double-click the dom.ipc.plugins.flash.disable-protected-mode preference to switch its value from false to true.

This might not take effect until all Flash has been unloaded for a few minutes, or you close Firefox.

Hotmail (Livemail) I think does not. At least not on the mail page. As to any messages being viewed . . . . .

FredMcD said

Hotmail (Livemail) I think does not. At least not on the mail page. As to any messages being viewed . . . . .

In case this helps solve it, it has only happened when I do not have an email open. Just the email homepage.

Hi keyser_soze83, did you try the malware cleanup?

jscher2000 said

Hi keyser_soze83, did you try the malware cleanup?

I did not. I did Adaware and CCleaner. Are you referring to Malwarebytes' Anti-Malware: http://www.malwarebytes.org/mbam.php from above?

The first two programs listed in cor-el's reply are a good starting point. They both have free versions which do not solicit payment for cleaning.

Thanks. I'll give those a shot when I get home. Again, in the effort to help this effort, here is the only link that I found when I Googled the error, and it is on a Mac. http://answers.microsoft.com/en-us/outlook_com/forum/opersonalization-oother/unresponsive-script-in-advert-driving-me-nuts-how/ca603eaf-c9dd-4ffb-94a3-ca7ada8de326?auth=1

Thanks again for all of the help and suggestions.

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.