From the past three days i have been really tearing my hear out trying to get the YouTube application working on my XBOX 360.unfortunately i do not have a permanent fix for this but you can try one of the below as a workaround one of the following should definitely work
- Go to your YouTube account login click on settings on the top right side of your YouTube userid--->Select MY Channel---->click on channel settings on the left hand side and rename your channel,Description and the tag and try to load the YouTube application once again.
- If the above does not seem to work go to your Xbox dashboard and try changing your gamer picture and your personal picture and try again.This is a silly fix but has shown great results to many!!!
- If the above does not work either..Change your gamer,Personal picture once again from your Xbox dashboard select party--->Start a party try once again.