System: Dell HP-Pavilion Windows 10 Ver.1607 14393.321 Firefox Ver. 49.0.2
Recently, after Windows 10, Firefox, and Adobe Flash October 2016 updates, my Norton Safe Search (NSS) in Firefox has stopped downloading & playing videos when searching with the "Videos" search option. I can use NSS to search for videos and I get the list I want, but when I try to play a video in NSS the operation hangs/freezes without downloading and without playing although the selected video is highlighted in green and the icon says "Now Playing", same as always. When using the "Web" search option in NSS to find videos (not as efficient, but you do get video hits), the video will download and play just fine as it always has. Videos also download and play just fine when using YouTube to search and play.
NSS on my Acer laptop with the same Windows version/build and same Flash & Firefox versions works just fine for searching, downloading, and playing videos using the "Videos" search option in NSS.
Using "copy link location", I can see that video "links" in NSS in the "Videos" search mode are Javascript commands while the video links in NSS in the "Web" search mode are URLs. I checked in Firefox about:config and found javascript.enabled=true. My ad blocker is not the problem because it is turned off on the NSS page.