This issue can be caused by an extension that isn't working properly.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

The above suggestion was tried but instead of Firefox starting in Safe-Mode, it started using Chrome and IE10 and I couldn't solve the issue.

Could be this bug:

• bug 1066934 - FF32: Skinned scrollbars thumb disappear upon scrolling a page at specific zoom percentage (different between FF themes)

Please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html

I once had that problem. Never did find out why.

One day, I decided to reset Firefox because of a different problem. After Firefox restarted, the scroll bars were normal again.

If you want to try this, backup your profile first.

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

Thank you for your suggestion to use FEBE. I did and backed up Firefox then did a reset and Firefox restored to its default setting and the scroll bar worked fine. Then I used FEBE to restore Firefox to my prior config- uration and it didn't work. I had to manually download and install my add-ons. The scroll bar still disappears when pressing on up and down. Firefox is still not restored to its original configuration. If you can offer another solution or correct what I have done, I'd sure appreciate it. By the way, there's an old Firefox data on my desktop in a folder. I don't know what to do with it or use it to put Firefox back to its original config. I'd still like to fix the disappearing scroll bar.

Hmm. Reset Firefox fixed the issue, but restoring brought the problem back.

Its one of your settings, or an add-on.

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. 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.

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

Hi, it's the Appearance Themes: Walnut and Walnut2, both v2.0.28 latest. I'm running Firefox in the Default Theme v32.0.3 and the scroll bar stays. Curious though, I've never had a problem with Walnut2 until v32.0.0 of Firefox release. What to do now? Thanks so very kindly for your help.

Great to here. Now please do two things. First, contact the home site of the theme. Explain what happened. Two; please flag your last post as Solved Problem to help others.

Happy Computing.

Hi again, I can't find the e-mail address for the Author of the Walnut and Walnut2 Appearance Themes. Would you please help one more time?

Check this link;

https://addons.mozilla.org/en-US/firefox/search/?q=Walnut+&appver=32.0&platform=windows

You can find the email address of the author (alfredkayser) on the Walnut2 page.

• https://addons.mozilla.org/firefox/addon/walnut2-for-firefox/

Hi, no go with the link. On my desktop there's an icon entitled: Old Firefox Data; how do I restore it to Firefox? It contains all of my customizations and configurations. I'll continue to use the default appearance theme till I find the Author's e-mail address and let him know about the bug in the themes. I can't thank you enough for your help.

Someone else posted a link that will give me Alfred Kayser's e-mail address. I'll try it out.

https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile

http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Hi, thanks for the URLs. Alfred Kayser, the author of Walnut/2, e-mailed me and said that Mozilla broke Firefox v32.0.0 and it will be fixed in v33.0.0. Thank you kindly for all your help.

That is likely the bug I posted above that affects Firefox 32 and is fixed in Firefox 33 and later.

• Bug 1066934 - FF32: Skinned scrollbars thumb disappear upon scrolling a page at specific zoom percentage (different between FF themes)