To continue: I also closed and re-started Firefox one time. It seems like I can now no longer use the option of typing "about:sessionrestore" in the address bar.

This can be a problem with the file sessionstore.js and sessionstore.bak in the Profile Folder

Delete the files sessionstore.js and sessionstore.bak and any existing files sessionstore-##.js with a number in the left part of the name like sessionstore-1.js .

Session restore works more reliable if you choose Tools > Options > General > Startup: "When Firefox Starts": "Show my windows and tabs from last time"

See http://kb.mozillazine.org/Session_Restore

Other things that need attention:

Your above posted system details show outdated plugin(s) with known security and stability risks that you should update.

• Next Generation Java Plug-in 1.6.0_14 for Mozilla browsers

Update the Java plugin to the latest version.

• http://java.sun.com/javase/downloads/index.jsp (Java Platform: Download JRE)

I've found the profile folder. It has only a sessionstore.bak file. There is also a sessionstore file which is a JScript file w/ no identifying type of file extension.

Just to be sure, I have re-started Firefox twice now so yesterday's lost session is not the 'prior' session.

If I proceed deleting the sessionstore.bak file, where will that leave me?

TIA