I suffer from the same problem, whatever browser I use, flash plugin raises the CPU usage permanently until I leave the web page. I f I turn disabled the plugin the problem dissapears, but, of course, the flash applets can´t be seen.

Moreover, a high and maintained cpu usage results in a high cpu temperature and eventually a system crash.

As a test, you can try this web page: http://librodenotas.com/deloanimallohumanolodivino/15934/la-mas-animal -de-las-musicas that contains severals youtube videos inset, even they aren't being displayed.

I've try disabling the "hardware acceleration" option (right click the flash and select "configuration") with no results.

Also I reverted to flashplayer 9 http://kb2.adobe.com/cps/406/kb406791.html but the problem persists.

Thank you It solved with me

To make clarifications for my previous post (some people emailed me saying that the link says nothing about cpu hogging or excessive cpu usage), you may not visit the LINK previously provided and instead follow the steps given below.

I would also like to point out my kind of problem that these steps successfully solved. The problem was this:

The first time I start up a browser (IE, FF, Opera, or Chrome) and visits a website with flash player files running on it, the performance of my
computer is smooth and fast for the first 2 or 3 minutes. But afterwards, the CPU usage meter just suddenly shoots up from below 10% to a shocking
100%! And there was not other program opened, except the browser; and I was only visiting one website ( e.g., Youtube).

It then clearly indicates that flash player is the culprit, since I have already run windows updating, spyware and antivirus scanning, defragmenting,
browser cookies and cache clearing, junk cleaning, and drive checking. I have also tried uninstalling and reinstalling flash players, which was actually
a good thing except that during that time I have not yet known about the next 4 steps (given below).

If you have the same problem, you might try th following:

NOTE: Close your browsers and any other running programs and opened windows first.

STEP 1: Navigate your way to this folder: Computer > C: Drive > Windows > System32 > Macromed > Flash

STEP 2: Right-click over the file ‘Flash10a.ocx’ and choose ‘PROPERTIES’.

STEP 3: In PROPERTIES, choose the ’SECURITY’ tab > Click on the ‘EVERYONE’ account or your own Windows account profile, and the button called 'EDIT’ and then tick the box called ‘ALLOW FULL CONTROL’ and also choose your own Windows local account name to have full control.

STEP 4: Repeat this process for the file ‘FlashUtil10a’.

Open a browser and check the performance of your CPU.

PS:
The example here indicates that the flash player version is 10; however, you can still use the steps for lower versions. For instance,
if the version of your flash player is 9, look for all files named FlashUtil9a (disregard the extensions).

Also, the Folder Directory is applicable for Vista users. The file directory structure of your drive C:\ may be different if you are using other windows OS version. You just have to search the location of your Flashplayer.

To:

montian and franky --- i'm so glad this procedure helps you with your prob!

have the same problem over here. I hate to dive into complexity  regarding this, but there are two things happening that might be  relevent. Firefox when examined with process monitor seems to be  recursively creating and killing threads which accounts for upwards of  20% of the cpu usage, these extensive bouts of activity are preceded and  punctuated by queries, read, and writes.

Thank you a lot.

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