Thanks for your post and welcome!
What source are you streaming from? It could be they have changed their links and for instance included a higher bandwidth stream which is not supported. Could you provide us with some more information please?
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Download Opera Mini from the Nokia Store. Then open the YouTube in it. Open video you want to watch. It'll work.
recently i have purchased nokia c2 03 which is not worth for my money it has several issues regarding the streaming of youtube videos kindly provde us the update for that via bookmark.