Just wanted to add that I am using a MAC. If I open YouTube on Chrome or Safari, it works fine. If I try clicking on embedded YouTube links on sites like Facebook, the video plays fine. If I open other sites with Flash (for example, www.espnfc.us or www.espncricinfo.com), they work fine too. I have noticed Firefox crashing only for www.youtube.com videos so far.

AppKit 

The crash report flagged these programs; VideoDecodeAcceleration AppleGVA libsystem_c.dylib = ? Word for Mac CoreFoundation CoreVideo Foundation CoreMedia VideoToolbox libsystem_pthread.dylib = ? Word for Mac libsystem_kernel.dylib = ? Word for Mac AppKit libobjc.A.dylib = ? Word for Mac http://support.microsoft.com/kb/2693802/en-us libdispatch.dylib = ? Word for Mac libsystem_malloc.dylib = unknown Mac ? ------------------------ For some time now, a lot of Mac’s with Microsoft programs have been crashing. Check with Microsoft / Mac support sites. ---------------------- If you have problems with current Shockwave Flash plugin versions then check this: * see if there are updates for your graphics drive drivers '''https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration''' * disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later) '''https://forums.adobe.com/message/4468493#TemporaryWorkaround''' * disable hardware acceleration in the Flash plugin '''https://forums.adobe.com/thread/891337''' See also: * '''http://kb.mozillazine.org/Flash#Troubleshooting'''