Flash is the most unsafe and unstable plug-in you may ever see. Disabling DEP may not be safe, because maybe there's a Flash security hole that is being used by a virus to get to your kernel. Recent crashes of certain multimedia contents (this includes Youtube videos, certain flash games and other applications) in conjunction with Firefox 15 are most probably caused by a recent Flash 11.4 update and/or a malfunctioning Real Player browser plugin. In order to remedy the problem, please perform the steps mentioned in these Knowledge Base articles: [[Flash Plugin - Keep it up to date and troubleshoot problems]] [[Flash 11.3 crashes]] [[Flash 11.3 doesn't load video in Firefox]] Other, more technical information about these issues can be found under these Links: http://forums.adobe.com/thread/1018071?tstart=0 http://blogs.adobe.com/asset/2012/06/inside-flash-player-protected-mode-for-firefox.html If Firefox (not Windows) lets you send a crash report to Mozilla, please do so and go to about:crashes and send us a crash report ID. Please tell us if this helped!