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Firefox 3.6.6 loads Flash webpages very slow



Just reporting issues with the latest Firefox 3.6.6 release where it does not load heavy flash use pages well at all. See www.tsn.ca for an example. It takes 20-30 seconds to fully load the TSN homepage which I noticed started occurring after I had updated to the latest Firefox version. I had the latest Flash plug-ins installed so that wasn't the problem.

I uninstalled Firefox 3.6.6 and located my previous Firefox version 3.6.3 and installed that which totally fixed that issue in loading any Flash websites. Must have been something that was changed in the latest release.

Others I am sure have reported this issue but thought someone should know....to hopefully work out the bugs/issues.

URL of affected sites


Chosen solution

Well, the x64 Win7 is not so flawless anyway... i experienced some other issues not only with FF & Flash.

As Kendal recommends, use in the meanwhile a previous version or a beta, i'm using now 4.0b1 and all my settings, addons and flash are working pretty good, also you can keep the 3.6.x version without any conflicts :)


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  • -getplusplusadobe16263
  • Adobe PDF Plug-In For Firefox and Netscape
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  • NPRuntime Script Plug-in Library for Java(TM) Deploy
  • The QuickTime Plugin allows you to view a wide variety of multimedia content in Web pages. For more information, visit the QuickTime Web site.
  • Shockwave Flash 10.1 r53
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  • BlackBerry WebSL Browser Plug-In
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  • Next Generation Java Plug-in 1.6.0_20 for Mozilla browsers


  • User Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv: Gecko/20100401 Firefox/3.6.3 ( .NET CLR 3.5.30729; .NET4.0C)

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Question owner

windows vista 64 user with 4gb ram. firefox sluggish with flash or javascripted websites. firefox uses 2gb of memory when visiting such sites. i suspect memory leak in 3.6.6.

Question owner

I have a similar problem.

Also, having problems with Yahoo email...sign comes up saying something like..."problems loading, try later."

I like FireFox; but lately, am having problems with certain websites slow to load. I am thinking about going back to an older version of FireFox.

Question owner

Também notei que depois que atualizei o Firefox p/ versão mais recente as paginas estão demorando p/ cerregar...espero que consigam resolver o problema.

Question owner

I also noticed this slowdown with several pages.

Question owner

Here's a snapshot of the error message I get sometimes when I use Firefox 3.6.6 to go to Yahoo email......

I then have to use another browser ....like Microsoft's IE browser to get into Yahoo email.

Hope this gets fixed.

Question owner

I have been getting very large memory leak issues.. doesn't matter which sites it seems like.. but it just will lag out the computer. I look at the memory usage on Firefox and it's sitting around 1 gig!

Got like Google Voice begin_of_the_skype_highlighting     end_of_the_skype_highlighting, Facebook, Gmail and a Wiki page open and it started doing it to me.. had it happen with other tabs before open.

Firefox 3.6.7 please come out soon and fix these issues!

Question owner

Firefox 3.6.6 on windows 7 64 bits.

Same problem here.... flash is sluggish since the last firefox upgrade.

Question owner

Same problem - Firefox 3.6.6 on Windows 7 64bit

Since the update Flash pages are sluggish. TSN.ca is a great example because it is unsurfable (I think I just made up a word) in Firefox 3.6.6

I too suspect a memory leak in either Firefox itself or the plug-in wrapper as when I go to TSN.ca 50% of my CPU is being used between both FF and the wrapper (25% each). When no Flash sites are up it's @ maybe 1%

Question owner

Yes I indeed have the same issue, I noticed it right after the update. The video section of CNN, and even embedded YouTube videos make the browser very slow.

Win 7 64

Question owner

Browsing performance becomes sluggish with 5+ tabs , left open for some time. Definitely a case of memory leak!

Close a few tabs and it becomes normal again.

@Folks at Mozilla

Please do your best to fix this at the earliest. TIA!

Question owner

^ In addition to the above reply, I use FF 3.6.6 on Win XP 32 bit.

Question owner

Same problem. Many video sites will play videos, but will not display thumbnails after upgrade to 3.6.6.

Question owner

Firefox 3.6.6 and Flash 10,1,53,64 Win 7 64bit. i5-750 4GB

Flash in firefox puts processor > 50% usage.

Flash content very slow/choppy. I would guess 50% frame rate drop over firefox 3.5.10. Downgrade to 3.5.10 fixes issue.

Same on my Mac Book Pro. Firefox 3.6.6 and Flash 10.1.X. Maxes intel dual core processor out.

Youtube choppy. Flash heavy websites extremely slow loading.

Safari, Chrome and IE all work fine with Flash 10.1

Question owner

Same behavior and specs as Kendal

Question owner

Same problem. Installing older adobe flash helps to fix it in about 30% :P. Might be something both with FF 3.6.6 and Flash 10.1 r52.

Question owner

yes , some youtube videos not working with firefox 3.6.6 !!! solution???

silkphoenix 92 solutions 1250 answers

That has been discussed in many thread in this forum. Please read the following for temporary solutions:


Question owner

adding to my earlier post: perhaps the problem is Firefox is not threading properly. I upgraded to the beta version of 3.6.7 and while it solved some of the issues with some of the sites - when I went to TSN (my new test site because it's so flash heavy) it was still extremely sluggish.

Now what led me to believe it's a threading problem.

I had to format my parents old Dell Dimension 8200 and reinstall everything. I installed 3.6.6 and 10.1.. of flash and it works like a dream. TSN is fast, youtube is fast - just as I would expect Firefox to run

Question owner


I tried disabling OOPP and restarting Firefox 3.6.6. No change. Flash content is still insanely slow. Tried the newest Adobe 10.1.8x beta release. No difference.

I went back to Firefox 3.6.3 trying both Flash versions. Flash content now plays at a reasonable frame rate. I went back to Firefox 3.5.10. It seems slightly faster with Flash content.

I also tried the latest Safari and Chrome to compare(using same flash). They were always faster at playing flash content than with the 3.6.x browsers. 3.6.3 can display flash at a reasonable frame rate, but 3.6.6 stutters and freezes constantly. They also don't use up >60% of my i5-750 like 3.6.6 does.

I also disabled hardware acceleration on flash. This actually made it worse. I have a debug version of the beta Flash 10.1.8x if there's any testing I could do with that to be helpful.

Mouse click is also not recognized very well or has a delay.

Is there an actual bug ticket for the slow framerate/stutter/whatever you want to call it with Flash?

Has there been contact with Adobe? Is it an adobe issue?(doubtful since safari/chrome/opera are okay with it)

Is there any information we can provide that will be helpful?

Is there a diagnostic tool that might provide more information to help with this?

Thanks, Kendal

Question owner

It also crashes them! It's the stupid plugin-container.exe that causes the trouble.