Hi,
We have just pushed an update to Google Webstore (1.17.1) which will fix a bug that was just found.
Since 1.17.0 there is a new settings panel where you can turn off any feature for any site by adding the site to the Blacklist.
Click the “S” logo in the extensions toolbar in chrome, click the small “Smuuvr Options” link at the bottom of that popup menu, and it will take you to the settings panel where you can add youtube.com to the blacklist and it will not run there anymore.
Thank you for the feedback!