Don't know what version of IE you are using ?
Or if you have tried this - disable the avast online security add-on in IE and see if that helps.
I rarely if ever use IE and on this XP system it only goes up to IE8 and by all accounts early IE versions aren't having so much of an issue. But later versions if they have the IE advanced protection setting (or what ever it is called), you could try disabling that as another option to try.
Now using IE11. This post was put up when I was on IE10. Iv tried disabling 'Protected Mode' with no effect.
As of late, on rare occasion I can get one or two YouTube videos run but that's it.
Same as DavidR, no problems with YouTube using XP, IE 8 and Avast 9.0.2008. Many YouTube videos are now in HTML 5 format which IE has never been good at. You can test IE and other browsers for compatibility at http://www.html5test.com/.
Tried turning the player to HTML5. It changes back and bam!!! When I can make it play the HTML5 version they play just fine, of course.
I understand a lot of you don't use IE. However, I have some sites that I need IE to use. Personally, since Google sold my data to the NSA; I don't have much love for their 'open source' projects anymore. And it was Google, not the NSA. The FISA court simply requested something Google agreed to give voluntarily to get some federal cash for one thi8ng or another. One look at the link in my signature proves that. My ISP didn't have to bend over for FISA one time... but that's a topic I think most should examine on their own.
Its not that I wear a tinfoil hat... its about integrity and standards and how a company treats MY personal data.