One potential cause of this is an unwanted extension. Try disabling ALL nonessential or unrecognized extensions on the Add-ons page. Either:

• Ctrl+Shift+a
• orange Firefox button (or Tools menu) > Add-ons

In the left column, click Extensions. Then, if in doubt, disable.

Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

If you are adventurous about installing software from various websites, you may have loaded a bundle that contains some, well, crap. To review recent additions, go to your Windows Control Panel, Uninstall a Program, and click the "Installed on" column heading to bring the most recent items to the top. Remove anything unexpected or unwanted.

Success?

I should add: to quickly and temporarily deactivate all extensions, you can use Firefox's Safe Mode.

Help > Restart with Add-ons Disabled

In the dialog, click "Start in Safe Mode" (not Reset)

If that stops the torment, you can go through the Extensions list as noted in my earlier post.

I did download a pdf converter from http://www.doc2pdf.net/. I've had about 20 different sites opening in new tabs. I've uninstalled this pdf converter program. Hopefully this solves the problem.

Thank you very much, Rudy