Originally Posted By: Bob_00001

Edit:
I figured it out. I overlooked the Settings button for the "Clear history when Firefox closes" option. Under Settings... you can choose whether or not to clear cookies. I turned that off, and now things work as they should.

You beat me to it. That's exactly the 'fix'.
(I've been preoccupied with my own issues involving upgrading and only just came across yours with respect to Firefox.)
I find Firefox just superb since way back when (eg, Netscape, Mozilla).
When you get comfortable with it and want to check out all the various configurations you can manipulate, go to about:config and have a boo.