It's possible that you are having a problem with some Firefox add-on that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?

Whenever you have a problem with Firefox, whatever it is, you should make sure it's not caused by one (or more than one) of your installed add-ons, be it an extension, a theme or a plugin. To do that easily and cleanly, run Firefox in safe mode (don't forget to select Disable all add-ons when you start safe mode). If the problem disappears, you know it's from an add-on. Disable them all in normal mode, and enable them one at a time until you find the source of the problem. See this article for information about troubleshooting extensions and themes and this one for plugins.

If you need support for one of your add-ons, you'll have to contact its author.

If the problem does not disappear when all add-ons are disabled, please tell me, so we can work from there. Please have no fear of following my instructions to the line, as all can be easily undone.

Thank you so much for offering your tips. I followed your suggestions and found the problem to be "seemingly" intermittent. However, i believe i've identified my folder of bookmarked tabs as the culprit. Before powering down for my Uverse install, I "bookmarked all tabs". It seems like FF works all the time, unless i call up the folder of 7 bookmarked tabs. If i call them up i have issues... if i just open up 10 other tabs... seems no problem. For now, i'm assuming it's problem solved as i'll simply call up each one of those saved tabs separately and assume the issue disappears. Thank you again for your time. I have nothing to offer but "thanks" and home handyman questions if there are any... :-)