Let me be the next to pile on. Using Vista and FF has been drastically slowing down since 3.4, if not earlier. I'm with a SaaS company that reeducates/harps on our customers to ditch the Jurassic IE and get FF...well I can't even use FF anymore because it is so slow just to start-up.

I hate to be a hater (what?) but Chrome has been getting the majority of my usage over the last few months because of this. AND I am flat out stopping use of FF until this is fixed...so all of my customer demos will highlight using Chrome first and FF/Safari as a secondary options over IE.

Sorry but ya'killin me with these "improvements"

I have the same problem, FF 3.6.6 is excruciatingly slow. At first I thought it was my wireless router, so spent 45 minutes on the phone with verizon....all to find out that Safari works just fine, it is just FF with the problem. PLEASE SOMEONE AT FIREFOX FIX THIS!! I am using Safari in the interim, but Safari does not play nice with certain websites yet, so I have to open FF for those sites......we need a resolution to this.

Hello again! FF 3.6.2 was also a fail...same bug...100% CPU load when opening other apps (Media Player Classic, ...) or typing this message now.

Thanks for nothing Mozilla!

Firefox 3.6.6 is 100% garbage. It's screwing up virtually everything on my computer in one way or another.

I can't even watch YouTube vids since Mozilla updated me to 3.6.6

I am unable to fill online forms with 3.6.6. It's terrible slow even if I want to scroll the page. The CPU usage is extremely high for 1 open tab.

I found that there's a fork of Firefox, called "Pale Moon" (google it, since non-Mozilla links get deleted by the mods). It's the same codebase as Firefox, but optimized for speed. Sadly, it's Windows only. There are similar projects for Mac and Linux, but I don't know much about those. And it doesn't support Athlon processors, either.

But if you have a non-Athlon Windows machine that's been hit by this 3.6.6 slowdown, give it a shot. It worked for me. The most recent build of Palemoon is based on 3.6.3, which predates the plugin-container.exe implementation in Firefox.

Since it shares the profile with Firefox, no data is lost. However, you do have to re-install plugins (just use FEBE/OPIE and you're done).

Now, I've got both Firefox 3.6.6 and Pale Moon 3.6.3 running on the same PC, and can switch back and forth (haven't tried running them concurrently, that might be a problem). Running the same plugins with the same settings and the same Flash plugin, Pale Moon is quite usable, while Firefox is pitifully slow, to the point where it's unusable. Pale Moon uses 200MB for the same tabs that Firefox/plugin-container eats 3.1GB of memory to load. And to think I used to complain about the 200MB usage.

The only (minor) annoyance is that because they are different versions, every time Pale Moon starts up, or at least every time it starts after Firefox has run, it checks that all plugins are compatible with it, which takes a few seconds. At least the portable version (which is what I'm using) does.

It's a price I'll gladly pay, given the alternative. A five second delay to load a version of Firefox that runs 100 times faster and takes one thirtieth the memory footprint? Yeah, I can deal with that.

Anyway, until/unless Mozilla comes out with a 3.7.x or whatever that addresses this issue for those of us that have it, maybe this can help at least some of the people whose Firefox has become unusable.

This is awful! I cant deal with it anymore. I'm sorry, I was a huge firefox advocate but this speed feels like dialup! using a macbook pro

Created & tried a new, fresh profile with FF Profile Manager. Same plugins as the old one, but no installed extensions. No problems so far!

So there must be a conflict with some add-ons.

Before blaming Mozilla, we should bring it to a common denominator?!

Here's my list of installed extensions:

- Flashblock 1.5.13 - Live HTTP Headers 0.16 - Cookie Monster 1.0.2 - NoScript 1.9.9.98 - BetterPrivacy 1.47.4 - Tab Mix Plus 0.3.8.4 - DownThemAll! 1.1.10 - Greasemonkey 0.8.20100408.6 - User Agent Switcher 0.7.2 - Selection Links 0.0.4

Man, the day I loaded Firefox my browsing problems seemed to go away for the most part. They'reee baaaack. From the moment I installed this (sigh) update, I entered browsing hell again. Not just slow but incredibly slow, also having more probs than ever before with page timeouts. I went from super fast to almost not being able to use the browser. the 3.6.6 is very very sick. Please fix this - I want to go back to my old firefox.

Same problem here. Are firefox going to even acknowledge this? I run my own business and would never let down my customers like this it is a disgrace. Is it too much effort just to post a quick message saying were looking into it?

Such a shame but i guess all good things to come to an end. As much as i hate to leave firefox it's google chrome for me from now on at least until this issue is fixed, but then again i might forget to even check if it has been fixed if google chrome keeps doing what i need it to and it just lets me browse without getting in my face like firefox is now.

The guy above who listed his add ons saying that might be the issue is wrong i have none of the add ons that you have mate. Bye bye firefox it was good while it lasted.

I have the same problem. 3.6.6 even refuses to type out the first 11 characters of this response. I canceled the cable and satellite services and so Flash (love it or not) is being used to provide all my TV/entertainment needs. A dedicated media computer with 2 GB of RAM and FF should take care of this function but with the problems I had to switch to Songbird or Opera or Chrome.

1) It is incredibly irresponsible for anyone to suggest turning off our security features when 3.5.x worked fine with the same features. I am not passing my credit card information through FF without security running.

2) Many machines still come with 2GB of RAM and it is no excuse for 3.6.6 to take up 1.4 GB (including the plug-in container) when the same tabs took 900MB on 3.5.x. This is with the BarTab add-on installed which is unloading pages that are unused for over 3 minutes.

3)There is no need for a plugin container if each tab was a separate process. If flash dies on that tab it doesn't effect the other tabs. Problem solved.

4)Firefox needs better memory management. It should be able to manage up to 1GB cache and keep it defragmented so that on 2GB machines tabs can be swapped out and in quickly.

5)FF needs a Bar Tab built in extension to offload idle tabs to the cache and out of RAM. I don't mind waiting a few seconds for an idle tab to reload because I know it is saving me RAM and I expect that initial delay.

I'm going back to 3.6.3 or earlier and maybe to 4.0b1 but that scares me more.

I'm running Windows 7 (64 bit Home Premium) and get the same problem. I thought there was something wrong with my computer at first since it's only a few days old. I get loads of not responding windows and it just takes forever for the page to finally load. I downgraded to 3.5.10 and it seems to work fine for now even if it's still a bit slower than I expected. If Firefox keeps being this horrible I might go back to IE and I haven't used that in years except to go on one site for university that's only compatible with IE.

I thought it was just my computer but I'm going nuts with FF and trying to load web pages! Are they going to fix this? Why do we have to try and fix their problem ourselves?

I just wanted to ad that I have no plug ins, unless FF did it automatically. I also wasn't running any videos at time of installation. I've been resorting to IE but maybe I'll try Chrome. Please fix FF!

i switched to Google chrome it was developed by some of the Firefox team that left them. its really good and i like it give it a try.

I'm trying Chrome right now. So far, so good!

Well, that's weird! I did a reply and Tony's name was used.

that is wired

Yeah, what a solution...use Chrome and share your private data with Google!

But in one point I have to agree: It's NOT the users responsibility to fix a problem they didn't cause. That is the responsibility of Mozilla and I still see no official statement here.

But instead of keep whining, please try a new profile and restore your settings of the old one following this guide. Let me know, if this gonna help you...(and I'm not the only one)

what private information? my bookmarks? my browsing history? LOL I have nothing to hide. Nothing is private in todays social media space/ todays technology etc. It's obvious that firefox has gone to shit and I'm glad I jumped off of it. It literally stalled everything on my machine. Chrome is super fast. what a relief.