[SD]draquish wrote:
Either downgrade to IE6.
Or switch to
Opera.

Both worked for me.
Not really a solution - youtube is supposed to work just fine with IE7 (it does for me).
I suppose you can downgrade to IE6 and see if it works. If it does, then either leave it at that or try upgrading again to IE7 - there might have been a problem with your download/installation of it.
If it doesn't work with IE6, then you might have installed something else along with IE7 that messed it up. If that's the case I can only recommend formatting

, unless you know what the additional things you downloaded and installed are, and can remove them