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I am desperate... Please help me with this problem

Every time I launch a YouTube video in Safari [5.1 (7534.48.3) / Lion OS X 10.7.1] the YouTube page is served and the video starts (sound included). With a short delay a second audio stream of the same video is served. When I stop the video player, the second (i.e. the delayed) audio stream continues. After closing the browser tab the audio stops. I can demo this with this URL , but any YouTube URL will do. N.B. No other video playback apps are running and there is no difference when using Flash or HTML playback.

What can cause this behaviour and HOW do I get rid of it?

share|improve this question
Do you use third-party Safari extensions, plugins, Input Managers, SIMBL plugins, etc.? Can you reproduce this behavior on another user account? – Daniel Beck Oct 10 '11 at 11:54
I can't understand why I did not check the extensions before I asked for help here! :-( I disabled all extensions and the phenomenon vanished. I discovered that the extension FlashToHTML5 by Joris Vervuurt (@ caused the problem. Thank you Daniel for the hint. Problem solved! – Fred Zelders Oct 10 '11 at 13:55
I posted an answer. Please accept so the system can consider this problem solved. – Daniel Beck Oct 10 '11 at 14:31
Where/How can I accept the answer Daniel? .. I checked the checkmark in front of the answer. Is that what you meant? – Fred Zelders Oct 10 '11 at 15:47
Yes, exactly. Thank you. – Daniel Beck Oct 10 '11 at 17:06
up vote 1 down vote accepted

Disable all third-party Safari extensions and plugins, Input managers etc. and check if the problem disappears.

If it does, you can selectively enable and disable them to find the culprit.

share|improve this answer
That did the trick Daniel :-) I found the extension that caused the behaviour. The extension is called FlashToHTML5 by Joris Vervuurt » I uninstalled the extension. Problem solved! THANKS! – Fred Zelders Oct 10 '11 at 15:50

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