This appears to be a common issue that no one has a solution for.
When liked to a YouTube video on a forum, the YouTube video will come up in a separate window and will have no problem playing.
But once the video has finished playing, there is no way to close that window and return to safari.
If I double tap the home button, I can switch to safari but all I get is a blank white screen. Even hitting the back button, the web page stays blank. I have to completely close safari and reload the page.