After some overdue Windows updates, I got hit with severe hangs when opening any page with Flash media. The window frame controls (e.g., minimize) still worked, but everything inside was inaccessible for minutes at a time. Then I would get a dialog indicating that a script was running slowly and had the opportunity to stop or continue. I had already disabled hardware graphics acceleration in Firefox and Flash, so the logical next step was to disable the Flash Player's protected mode. That is described in this support article from Adobe under the heading "Last Resort": [http://forums.adobe.com/message/4468493#TemporaryWorkaround Adobe Forums: How do I troubleshoot Flash Player's protected mode for Firefox?] It worked. The Windows updates, probably only one of which is the culprit, were: * [https://technet.microsoft.com/en-us/security/bulletin/ms13-049 Microsoft Security Bulletin MS13-049 - Important : Vulnerability in Kernel-Mode Driver Could Allow Denial of Service (2845690)] * [https://technet.microsoft.com/en-us/security/bulletin/ms13-050 Microsoft Security Bulletin MS13-050 - Important : Vulnerability in Windows Print Spooler Components Could Allow Elevation of Privilege (2839894)] * [https://technet.microsoft.com/en-us/security/bulletin/ms13-047 Microsoft Security Bulletin MS13-047 - Critical : Cumulative Security Update for Internet Explorer (2838727)] * [https://technet.microsoft.com/en-us/security/advisory/2854544 Microsoft Security Advisory (2854544): Update to Improve Cryptography and Digital Certificate Handling in Windows]