User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.87 Safari/537.36 Steps to reproduce: 1)Start Nightly with clean profile. 2)Open www.youtube.com in new Tab. 3)Open a video. 4)Select different video from right side. Actual results: Firefox freeze for sometime.Then the new video is open. Expected results: Video should be changed smoothly.

Reproduced this issue, with the steps provided, on Windows 10 x64 bits, with Nightly 49.0a1: - Build Id: 20160426044609 - User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:49.0) Gecko/20100101 Firefox/49.0. The issue is highly intermittent, I only reproduce it twice. Could not reproduce on Firefox Release version: 46.0 Could not reproduce on Windows 7.

when you go to youtube.com/html5 what's the status for MSE/webm? if it's enabled, my guess is that it's a regression from bug 1257699 which will be fixed by bug 1261900

(In reply to Jean-Yves Avenard [:jya] from comment #3) > when you go to youtube.com/html5 what's the status for MSE/webm? > > if it's enabled, my guess is that it's a regression from bug 1257699 which > will be fixed by bug 1261900 Status of MSE/webm is disabled.

Is this still an issue? Can you link to a video that causes the problem for you?

Brindusa - is this fixed?

(In reply to Anthony Jones (:kentuckyfriedtakahe, :k17e) from comment #5) > Is this still an issue? Can you link to a video that causes the problem for > you? It is fixed now.

I have tested this issue on the latest Nightly build 49.0a1 on Windows 10 x64 and could not reproduce it. Based on this and on Comment 7 from the reporter, changing status to RESOLVED WORKS FOR ME.