Yes it happens on YouTube when u try to play the video under lock screen that is in IE11 in WP8.1! I get this error sometimes too! After u reboot ua device it will be fixed! Hope this helps!
Yeah !! I'm facing the same problem bro.. Wanna get rid of it.. I recently updated my Lumia 625 with Official release of LUMIA CYAN UPDATE BY NOKIA.. .. I waited n installed the official one and I am greatly disappointed
You have to reboot your phone. Video streaming is buggy on ie on 8.1. If you like streaming youtube videos I recommend using metrotube or mytube instead of the youtube websites.