I have excessive tearing while playing 1080p Flash Videos on youtube ! my graphic card is ati radeon hd 2400 , its old but on windows 7 i don't have tearing. Does ubuntu ALWAYS have tearing with any graphic card ?? Why they can't fix that ?

It works differently in Windows as Windows is a completely different OS with different support. Can you give the output of:

lsb_release -a; uname -a; dpkg -l | egrep 'flash|gnash|swf'

Thanks

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 11.04
Release: 11.04
Codename: natty
Linux darkpc 2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:24 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
rc flashplugin-installer 10.3.183.10ubuntu0.11.04.1 Adobe Flash Player plugin installer
ii flashplugin64-installer 11.0.1.129-0ubuntu0~sevenmachines1 Adobe Flash Player plugin 64 bit alpha installer

By the way i found the ati control panel and enabled the antitearing and everything works just fine !
But the problem is that i will install into my desktop a better graphics card geforce gts 250 and i'm afraid it will have tearing too even if its a good card , what can i do to stop tearing if i have ?

Also try to check this video and watch the first two mins and tell me if you have tearing i no longer have thanks to ATI control panel. :-)
http://www.youtube.com/watch?v=fYPAXkHGwoM

sudo dpkg -P flashplugin-installer

Will tidy up nicely. The 64bit for your 64bit OS is a great choice

Nvidia LOVE linux, their drivers have been phenominal the last 10 years I've been using Linux and it's all I buy. ATi have only just started coding for linux in the last 3 / 4 years. You should also uninstall the proprietary ati driver if you are replacing the card so it doesn't get the OS mixed up, same as you would in Windows

While I agree with actionparsnip that purging all files associated with the package flashplugin-installer is the first thing you should try, I don't agree that this will probably work. It's the first thing to try, but in my experience, this rarely actually solves the problem. flashplugin-installer is not actually installed, so while a conflict between its configuration files and the installed package flashplugin64-installer is possible, it's not particularly likely.

So after following actionparsnip's instructions, if they do not solve your problem, please make sure to change this question's status back from Solved to Open. (You had marked it as Solved in your reply to actionparsnip's first post.) To make this change, you can go to https://answers.launchpad.net/ubuntu/+source/flashplugin-nonfree/+question/172036, type your reply into the big text box near the bottom of the page, and click "I Still Need An Answer".