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some videos doesn hide the bar on the button of the bar and those videos runs slow in big and full screen, the others that hide the bar run slow only while the video is loadin all (gray line in the bar)

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ubuntu 11.10 firefox 10.0.2

this video for example doesn hide the bar for me and it runs always slow

http://www.youtube.com/watch?v=Dou4Gy0p97Y and this is the same video but it hides the bar and it run in 720p normal but! after charge all the video (the grey bar), if it is not charged at all it plays slow http://www.youtube.com/watch?v=lhoYLp8CtXI

ubuntu 11.10 firefox 10.0.2 this video for example doesn hide the bar for me and it runs always slow http://www.youtube.com/watch?v=Dou4Gy0p97Y and this is the same video but it hides the bar and it run in 720p normal but! after charge all the video (the grey bar), if it is not charged at all it plays slow http://www.youtube.com/watch?v=lhoYLp8CtXI

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oh i forget i test my firefox against opera and opera is winnin playin youtube .( plz help i love firefox

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What is the processor load when you experience such a slow down?

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes).

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i am using the deaful theme, this problem is new, a few days ago it doesnt happen, starts suddenly i am consedering a update bug or something or maybe something about htlm5 because vevo videos runs well when they are all charged xs any other idea. pd opera runs the videos almost perfect xs so the aceleration i amnot sure about it xs