Youtube unblocker was a malicious add-on. As soon as it's malicious activity was discovered we blocklisted and removed that add-on, however there is a possibility that some malware remains on your computer. I suggest you do the following:

• Troubleshoot Firefox issues caused by malware Run all the tools at the bottom of that page
• Refresh Firefox - reset add-ons and settings this will remove any last traces of youtube unblocker.

Are you still using the profile where this extension is located?

That profile got created Sun May 3, 2015 (1430664102640) as the result of a reset.

You can use this button to go to the current Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

to add to first part by Tyler see https://addons.mozilla.org/firefox/blocked/i1129

I didn't see any profile from 5/3/2015 - 1430664102640, so I guess it got deleted. I did a refresh on Firefox and deleted all my addons. Only a few addons were put back, but not YouTube unblocker. The only problem that I experienced was with new Tab, but that wasn't serious. Thanks for all your replies and help. len