If it worked just fine yesterday and doesn't today I'd investigate what changed (and it could be something outside of Firefox).

Try seeing if there are any Windows updates available, making sure you are using the latest graphics Driver version, scanning for malware, looking into your anti-virus, etc.

Hello,

To find the correct solution to your problem, we need some more non-personal information from you. Please do the following:

1. Use ONE of these methods to open the Firefox Troubleshooting Information page:
   • Click the menu button , click on help and select Troubleshooting Information.
   • Type about:support into the Firefox address bar and press the enter key.
2. At the top of the Troubleshooting Information page that comes up, you should see a button that says "Copy text to clipboard". Click it.
3. Now, go back to your forum post, right-click in the reply box and select Paste from the context menu (or else click inside the reply box and press the Ctrl+V keys) to paste all the information you copied into the forum post.

If you need further information about the Troubleshooting information page, please read the article Use the Troubleshooting Information page to help fix Firefox issues.

Thanks in advance for your help!

I've done nothing of interest on my computer, and other browsers are working just fine (Chrome, IE...), but I want my Firefox back. It is the Firefox process which is taking too much CPU, not any other process :

http://i.imgur.com/BS3IV8W.jpg

It shows 25% because it is a Quad core computer, it is taking 100% of 1 core.

Here is my Troubleshooting information :

Application Basics

Name: Firefox Version: 31.0 User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Firefox/31.0

Crash Reports for the Last 3 Days

All Crash Reports

Extensions

Name: Abduction! Version: 3.5.0 Enabled: false ID: {b0e1b4a6-2c6f-4e99-94f2-8e625d7ae255}

Name: Adblock Plus Version: 2.6.4 Enabled: false ID: {d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}

Name: avast! Online Security Version: 9.0.2018.95 Enabled: false ID: wrc@avast.com

Name: Classic Theme Restorer Version: 1.2.3 Enabled: false ID: ClassicThemeRestorer@ArisT2Noia4dev

Name: ColorfulTabs Version: 24.5 Enabled: false ID: {0545b830-f0aa-4d7e-8820-50a4629a56fe}

Name: Disconnect Version: 3.14.0 Enabled: false ID: 2.0@disconnect.me

Name: Empty Cache Button Version: 2.6 Enabled: false ID: {4cc4a13b-94a6-7568-370d-5f9de54a9c7f}

Name: feedly Version: 16.0.528 Enabled: false ID: feedly@devhd

Name: Firebug Version: 2.0.3 Enabled: false ID: firebug@software.joehewitt.com

Name: Gmail Notifier (restartless) Version: 0.4.6 Enabled: false ID: jid0-GjwrPchS3Ugt7xydvqVK4DQk8Ls@jetpack

Name: gTranslate Version: 0.9 Enabled: false ID: {aff87fa2-a58e-4edd-b852-0a20203c1e17}

Name: LastPass Version: 3.1.1 Enabled: false ID: support@lastpass.com

Name: QuickNote Version: 0.7.3 Enabled: false ID: {C0CB8BA3-6C1B-47e8-A6AB-1FAB889562D9}

Name: Troubleshooter Version: 1.1a Enabled: false ID: troubleshooter@mozilla.org

Name: YouTube High Definition Version: 31.2 Enabled: false ID: {7b1bf0b6-a1b9-42b0-b75d-252036438bdc}

Graphics

Adapter Description: AMD Radeon HD 7900 Series Adapter Drivers: aticfx64 aticfx64 aticfx64 aticfx32 aticfx32 aticfx32 atiumd64 atidxx64 atidxx64 atiumdag atidxx32 atidxx32 atiumdva atiumd6a atitmm64 Adapter RAM: 3072 Device ID: 0x679a DirectWrite Enabled: false (6.2.9200.16492) Driver Date: 10-8-2013 Driver Version: 13.152.1.8000 GPU #2 Active: false GPU Accelerated Windows: 0/1 Basic Vendor ID: 0x1002 WebGL Renderer: Google Inc. -- ANGLE (AMD Radeon HD 7900 Series Direct3D9Ex vs_3_0 ps_3_0) windowLayerManagerRemote: false AzureCanvasBackend: skia AzureContentBackend: cairo AzureFallbackCanvasBackend: cairo AzureSkiaAccelerated: 0

Important Modified Preferences

accessibility.typeaheadfind.flashBar: 0 browser.cache.disk.capacity: 358400 browser.cache.disk.smart_size_cached_value: 358400 browser.cache.disk.smart_size.first_run: false browser.cache.disk.smart_size.use_old_max: false browser.cache.frecency_experiment: 3 browser.places.smartBookmarksVersion: 7 browser.search.openintab: true browser.sessionstore.upgradeBackup.latestBuildID: 20140716183446 browser.startup.homepage: about:home browser.startup.homepage_override.buildID: 20140716183446 browser.startup.homepage_override.mstone: 31.0 browser.tabs.warnOnClose: false browser.urlbar.default.behavior: 2 dom.disable_open_during_load: false dom.mozApps.used: true extensions.lastAppVersion: 31.0 gfx.direct3d.last_used_feature_level_idx: 0 network.cookie.cookieBehavior: 3 network.cookie.prefsMigrated: true places.database.lastMaintenance: 1408381905 places.history.expiration.transient_current_max_pages: 104858 plugin.disable_full_page_plugin_for_types: application/pdf plugin.importedState: true privacy.clearOnShutdown.cookies: false privacy.clearOnShutdown.history: false privacy.clearOnShutdown.offlineApps: true privacy.clearOnShutdown.siteSettings: true privacy.donottrackheader.enabled: true privacy.sanitize.migrateFx3Prefs: true privacy.sanitize.sanitizeOnShutdown: true storage.vacuum.last.index: 1 storage.vacuum.last.places.sqlite: 1407535538

JavaScript

Incremental GC: true

Accessibility

Activated: false Prevent Accessibility: 0

Library Versions

NSPR Expected minimum version: 4.10.6 Version in use: 4.10.6

NSS Expected minimum version: 3.16.2 Basic ECC Version in use: 3.16.2 Basic ECC

NSSSMIME Expected minimum version: 3.16.2 Basic ECC Version in use: 3.16.2 Basic ECC

NSSSSL Expected minimum version: 3.16.2 Basic ECC Version in use: 3.16.2 Basic ECC

NSSUTIL Expected minimum version: 3.16.2 Version in use: 3.16.2

Experimental Features

Do I need to provide more info?

Did you install or update any new extensions?

You can check the update history on the "Firefox/Tools > Add-ons > Extensions" page via its Tools button.

Try to create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

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

cor-el thank you for your help.

I had the problem even in safe mode, so it is definitely not related to any addon.

Creating new profile and reimporting everything solved the problem but wasn't fun to do.