This worked for me on the Microsoft Community thread linked by sd173:
Open internet explorer then Tools
Then go to Manage Ad-ons
on the left hand side, go to Tracking Protection
Then find Get a Tracking Protection List online
When in this, change the top (Mine says Australia(English) to United States(English)
Go down this list to find Stop Google Tracking and Add it.
You can go back to Manage Ad ons to find this in the list.
After doing this I could watch You Tube videos again
Just another reason to hate Google.