Computer freezes when trying to view youtube etc videos

[#1]

My Dell Laptop has suddenly decided it will freeze everytime I try to view a video on youtube [or vimeo]. I use Windows 7 [64 bit] with Firefox as browser.  I have to use Task Manager to get out of the freeze.
Can anyone help?

[#2]

It may be a Flash Player problem.  Try uninstalling it then downloading and installing the latest version (11).  Also check that you have the current version of Firefox (7).

[#3]

I've noticed that, for some unknown reason, Flash Player 11 is screwing some streaming with FF and Chrome. So I have reverted back to 10.3.183.7 on my laptop which is W7 64bit.
You can get previous versions here.

[#4]

Very interesting!! I'm having similar problems.
I've just checked Control Panel and discovered I have 2 Flash Players installed:
Adobe Flash Player 10 Plugin v 10.1.85.3
and
Adobe Flash Player 11 ActiveX v11.0.1.152
Now if you select Support Information > Product Update for the Plugin it takes you to the download for 11.0.1.152.
I think I'll remove both of the above and then reinstall the latest version (11.0.1.152)  
Edit1:
Just done that with a reboot inbetween removal and install.
IE8 on my Dell Laptop with XP Home SP3 seems to run much faster. Time will tell!
Edit2:
Unfortunately, that hasn't solved the problem. It's happened again with Task Manager being the only exit. 

[#5]

You haven't said what processor is in use.
I have three laptops, the oldest one (with Windows XP) I would not even think of using for video.
The second oldest is an Acer 5101 with AMD Turion 64 running Ubuntu/Linux v10.04 LTS, it will handle ordinary video but not HD video.
The newest one is an Acer 5742 with an Intel i3 370m processor running Ubuntu/Linux v10.10, it will handle HD video with no problems.
On the AMD Turion 64 the problem with HDV is that that CPU cannot handle the size of file (HDV) within the refresh rate required, so causes a temporary freeze.

[#6]

Does it help if you disable Hardware Acceleration in Firefox? (Options, Advanced tab)

[#7]

CX23882's answer is what fixed the same problem on my Dell laptop. You can also disable it by right clicking on the flash video and choosing disable Hardware Acceleration again.

[#8]

Thank you for your suggestions - will try them out the next time it happens because of course since mentioning it - videos have been working!!