Same issue here - Firefox 3.6.6 (Windows Vista 32-bit) is extremely slow, CPU usage jumps to 40-50% on a quad-core box. This is particularly evident while accessing Javascript-rich websites such as Google Docs.

FF updated to 3.6.6, running fine for a day or two, then suddenly 99% cpu on a completely vanilla wordpress page (pressed back then refresh). Had to kill it. Haven't seen this behaviour since the separate plugin-container process was implemented.

Seriously, Firefox guys. I am downgrading mine back to 3.6.3.

I noticed as well that when this crippled version crashes, there is no crash reporter (incidental) and Firefox doesn't sheepishly offer to pick up where you left off when you restart.

Big problem. It was that "feature" alone that made previous crashes even bearable.

Listen up, users. Here's how I cope:

I have different versions of portable Firefox and I use each for particular purposes. I have a different plugin cocktail for each version. Rather than mess around with profiles and have one "master" installation, I just prefer to compartmentalize. When I accidentally "upgrade" because I thought it was an official update and not some alpha test "a la Vista" foisted upon an unsuspecting user base and gone horribly, horribly wrong, I can just trash the new, improved version in favor of an exact duplicate of my older, supposedly suckier version.

The poster talking about trying to jog on a treadmill underwater is dead-on with their assessment. It's like Winamp 3 and the "Thinger." That's what the stupid plugin-container.exe is. It's Firefox's Thinger.

Firefox? Bloatware? I think I'm gonna be sick! Get something for me to be sick in! Oh, God! Oh, my, GAWD!

After Winamp 3, those guys from Nullsoft sold out to AOL-Time Warner. There is no Winamp v4.

Can you please just fix it, please?

I have the same issue and its really annoying. Please fix this problem, why do u have to mess with it anyway it was working fine before.

Indeed, FF 3.6.6 is excruciatingly slow. It may depend on the number of tabs. I tend to have 30 or so tabs at a time, which was never a problem until now. Effectively the latest version of FF has rendered it unusable. Did the FF QA team run any performance regressions before releasing?

Yes, the problem is how THEY implemented the plugin safety inside Firefox.. creating another process, that is plugin_container.exe!! - infallible logic though!

The problem is, you want to make your product safe and sound.. please DON'T externalize sensible code inside another process so that "your product" is stable, let's blame the other.. which is not called firefox.exe!!

Nice recall about Winamp and the Thinker.. it came the 3 but NEVER the 4th.. would be the same for Firefox?

Just implement a lightweight structure for Flash, OR if you recognize Flash as being an unbearable weight to carry, EXCLUDE IT.. you won't be the first to do so ;)

Hint, rename the "plugin_container.exe" to "*flash_something_to_blame*" so the user will spam someone else forum instead :D

i notice that 3.6.6 is slow too , i use windows 7

CPU ussage indeed >90%. Does nobody of the FF-team react on this?

FF 3.6.6 hangs up when reproducing flash video. Only solution I found was to reinstall 3.6.3 and disable automatic update to 3.6.6

Mozilla guys, you should fix this, please!

Umm, I'm using XP and it has the plugin-container.exe in the windows process list when i run firefox. Actually when I installed this new version it always crashes the Adobe Flash Player, making the new firefox process of plugin-container.exe pointless. And I can't degrade my firefox to 3.6.3. Why?

Ever since my Firefox has been updated it has slowed down dramatically. No problem before 3.6.6 was upgraded. Apparently we have Farmville to blame D:

http://kotaku.com/5576118/we-all-had-to-update-firefox-because-of-farmville-users

same problem here - using ff 3.6.6 on mac os 1.6.4 / slow startup, browser freezes sometimes also it seems to slow down the whole os ...

FF 3.6.6 updated on 4 systems at home. All slow with FF 3.6.6. One XP, one Vista, and Two Win 7 machines. Phone calls up the ying yang from people wanting to know what to do. (I'm the family and friend career geek that gets the "HELP ME" calls when things go wrong)

Been having everybody back date.

change the hang detector setting dom.ipc.plugins.timeoutSecs; change it back to 10 instead of 45 - and you are done. That is the only change in the 3.6.6 release..

win xp sp2 the same happening to me since yesterday(update to 3.6.6)

My problem was very slow load up of Firefox 3.6.6 as I have already posted.Web pages taking an age to load.The web page slowness was also on on Google chrome and Internet explorer.

 After changing the LAN setting from Auto config script to Auto detect settings all three browsers are back in fast working order.I can only presume the Firefox update altered these parameters.I.m now a happy bunny.

Adobe Flash Player crashed many times. That's it, the plugin-container.exe is rather pointless! They should get it out as an feature of Firefox. Maybe it's the one who causes crashes. And BTW, the Firefox release notes says it has a protection feature to plug-ins, which makes this more pointless.

Extremely high CPU load with Flash enabled on Firefox 3.6.6. This is not seen before without Lorentz.

it freezes my whole computer and i'm forced to restart it i cant even ctrl alt del to get out of it just hangs. what a joke i'm thinking of going to safari.

Just adding my voice to the fray. Same problem. Takes forever to load web pages compared to chrome or previous versions of firefox.

A long thread in a forum can take 30+ seconds to load in firefox 3.6.6, where it will take 2 seconds in chrome.