The pop-up asking if I wanted to upgrade to FF 17.0 had a link to a warning that it might disable System Restore. I clicked “No” for the update not wanting to lose System Restore but 17.0 somehow loaded anyway. Since Mozilla techs knew that 17.0 could cause System Restore problems, I am hoping they will know how to fix them.
It might help if you could tell us which extensions you have added to Firefox, since one of those might not be compatible with Firefox 18. A list of installed extensions and other troubleshooting information can be copied to this thread as follows:
Click the Firefox button at the top left, then click the Help menu and select Troubleshooting information from the submenu. If you don't have a Firefox button, click the Help menu at the top and select Troubleshooting information from the menu.
Now, a new tab containing your troubleshooting information should open.
At the top of the page, you should see a button that says "Copy all to clipboard. Click it.
Now, go back to your forum post and click inside the reply box. Press Ctrl+V to paste all the information you copied into the forum post.
P.S. Firefox 18 is the latest version of Firefox. To stay safe online, you should update to Firefox 18. See Update Firefox to the latest version for detsiled detailed information about the update process, including screenshots.