Hi blebadef, Thank you for the description and the troubleshooting steps in your question. I understand that Flash video partially load, but do not play, and it only happens on one operating system on the latest version of Firefox and Flash. On the XP pro computer are your WebGL graphics drivers up to date? Is the plugin set to click to play? ("Always Ask" would be the setting on the page) Does it happen when Firefox hardware acceleration is turned off? You might need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.). Then perform these steps: #Open Firefox ''Options'' window (''Preferences'' on Mac or Linux) as follows: #* In Firefox 29.0 and above, click the menu button [[Image:New Fx Menu]] and select ''Options'' for Windows or ''Preferences'' on Mac or Linux. #* In Firefox 28.0 and previous versions, click the orange Firefox button at the top left, then select the "Options" button, or, if there is no Firefox button at the top, go to Tools > Options. #In the Firefox Options (or Preferences) window, click the ''Advanced'' tab, then select ''General''. #In the settings list, you should find the ''Use hardware acceleration when available'' checkbox. Uncheck this checkbox. #Now, restart Firefox and see if the problems persist. Additionally, please check for updates for your graphics driver by following the steps mentioned in the following Knowledge base articles: * [[Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems]] * [[Upgrade your graphics drivers to use hardware acceleration and WebGL]] Did this fix your problems? Please report back to us! Thank you.