YouTube stopped message

[AC Question]

my lenovo smart phone has come up with the message "Unfortunately, YouTube has stopped." I press OK but the message wont disappear. Nothing will work while this message is on screen, I can't answer a call etc.
Any ideas?

 

[B. Diddy]

Welcome to Android Central! Power the phone down (you can press and hold Power for 10-15 seconds to force a shutdown if you're not able to power down normally). Then power back on, and see if the same thing happens. If not, go to Settings>Apps, select YouTube, and Clear Cache/Clear Data. Now see if the problem comes back.