Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

[Use Hardware Acceleration] was already turned off. Thanks for the suggestion. I had not run across Hardware acceleration as a possible problem.

Did the problem go away in safe mode?

I'm hesitant to say the problem went away in safe mode because the FF window in safe mode requires resizing to fit the screen. When resizing the FF window in normal mode, the scroll bar and find bar suddenly appear.

    The short answer is yes, I've not been able to reproduce the problem in safe mode yet.  All I can say at this point is: the frequency of the problem is reduced and the resizing of the window could be effecting the results.  I will need to do more testing in safe mode which can be problematic because the window is so small.

During some additional testing, the default safe mode window was not changed or resized. The window is so wide, the horizontal scroll bars never appear because they never need to appear. Since adjusting the FF window fixes the problem, under this conditions reproducing the problem seems highly improbable.

In safe mode, the window is wide an there was never a reason to use the horizontal scrollbars but the Find bar did not appear after pressing Ctrl-F. The window bottom had to be pulled up and down in order to get the Find Bar to appear. The frequency of the problem was greatly reduced in safe mode. This is the symptom related to the Find Bar & horizontal scroll problem.

Type about:addons<Enter> in the address bar to open your Add-ons Manager. Hot key; <Control>(Mac:<Command>)<Shift> A)

In the Add-ons Manager, on the left, select Extensions. Disable a few add-ons, then Restart Firefox.

Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All of them.

If the problem continues, disable some more (restarting FF). Continue until the problem is gone. After, you know what group is causing the issue. Re-enable the last group ONE AT A TIME (restarting FF) until the problem returns.

Once you think you found the problem, disable that and re-enable all the others, then restart again. Let us know who the suspect is detective.

You can check for problems caused by a corrupted localstore.rdf file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

All the extensions were disabled and the problem still exists. FF was observed for several days to confirm the disappearing horizontal scroll bar and Find bar.

The "corrupt localstore.rdf" was found from another question. The manual solution was carried out. The localstore.rdf file has been rename several times. The xulstore.json file

I once had a problem with my scroll bar, but it was minor, so I did nothing. One day, because of another issue, I decided to Reset Firefox {web link} Once I was done, I found the scroll problem was gone.

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences

Creating a new profile was a good idea and is the solution of choice. In practice, some critical mistakes were made along the way, so FF environment is being recreated in the new profile. One critical mistake was failing to make a good backup. FEBE and OPIE could be better ways to backup FF. Backups are critical to successfully completing the move to a new profile. If I did this again, all three backup schemes would be done before creating the new profile. The new profile should have nothing in common with the old profile including the name and storage directory - [Choose a folder].

Use the Bookmark backup rather than "export bookmarks to HTML." Bookmark backup creates a json file that can be better imported into the new profile.

The solution now is to switch between the old and new profiles as needed. When creating the new profile be sure to uncheck the box next to "Use the selected profile without asking at startup." This will allow you to switch between profiles at startup. The older profile can be used when the new profile doesn't work right. Once the new profile has been updated sufficiently and you are no longer using the old profile then "Use the selected profile without asking at startup" box can be checked again.

Thank you for this solution. With some practice and in the future, the create a new profile is or will be a good tool.