I've been having this problem for awhile and I have absolutely 0 idea of how to deal with it. It just started one day- nothing having changed about my iPhone. I tried to watch a video through the YouTube app but every try gave me the same result of the video being unable to load and a little window popping up simply saying 'Unknown Error'. The same thing happens on my mom's iPhone, and my sister's brand new iPhone4. I have the problem in different locations as well. If anyone has a solution I would so much love to know it.