Sorry for the delay!
Unfortunately we aren't able to do phone support.
First make sure you have the latest version:
Second, can you describe exactly what happens when you download a file from YouTube and attempt to play it - does it play? What file type is it?
The next time this issue occurs, can you send the log file to us? You can find it by going to the Preferences and clicking Find Log File.
From Ben Graham @ 30 Sep 2015 13:09