Could you try disabling Firefox's hardware graphics acceleration? Due to some recent driver updates, many users are experiencing strange performance and stability issues linked to this feature.

You usually need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

orange Firefox button or classic Tools menu > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

If you restart Firefox, is the issue resolved or at least improved?

It is very minimally improved. The change is almost not noticeable at all. Also, when I closed Firefox and restarted it, I got popup messages saying that Firefox is already running even though it wasn't listed as a process in the task manager. This has happened many times in the past. I think after it popped up four or five times, it finally loaded. But it is still lagging significantly.

Nevermind, it's lagging even more now.

If you don't see Firefox.exe in the Processes tab of the Task Manager, but Firefox thinks it is running, this might indicate a locked file in your personal settings folder (AKA Firefox profile folder). This also may prevent settings changes from being saved. Can you confirm that hardware acceleration is off? You can check:

Help > Troubleshooting Information

Toward the bottom, in the Graphics section, Direct2D Enabled and DirectWrite Enabled should be false, and the number of GPU Accelerated Windows should be zero.

Yes, hardware acceleration is off.

A standard diagnostic to bypass interference by extensions (and some custom settings) is to try Firefox's Safe Mode.

First, I recommend backing up your Firefox settings in case something goes wrong. See Back up and restore information in Firefox profiles. (You can copy your entire Firefox profile folder somewhere outside of the Mozilla folder.)

Next, restart Firefox in Firefox's Safe Mode (Diagnose Firefox issues using Troubleshoot Mode) using

Help > Restart with Add-ons Disabled

In the dialog, click "Start in Safe Mode."

Does Firefox work any better in Safe Mode?

It works somewhat better, but it is still lagging a lot. What should I do?

Nevermind, it has not improved.

I am going to reinstall Firefox.

This seems to have fixed the problem...at least for now.

Some of the crash reports indicate a problem with the Java plugin (npjp2.dll and jvm.dll), so you can also check for problems with Java.

• http://kb.mozillazine.org/Java

I have updated Java on my system. I will see if this improves the performance of Firefox.

So it's not lagging as much but now every element on a page is loading very slowly one at a time.