In Firefox 39, there is an Addon called 'About:newtab', version 126.96.36.199.1 (signed) which I've been using and liked a lot. It allows you to pick a new tab wallpaper, and then your thumbnails in a set number of columns and rows.
Unfortunately, beginning with some Intel Windows update I got for Intel HD Graphics about two months ago, not knowing this add-on was the problem, FF started to run funny. Client of mine had the same problem, also using Firefox, so I advised him to avoid the latest Intel update via WU.
For Windows 7 would crash after being idle. This was with one monitor. After getting Windows back in Safe Mode, then rebooting normally: Firefox was unable to show the menu, but only the one tab, can't size the window nor access any options, as often happens if you let those nasty survey monkey windows pop up. So, since that was what had just happened prior to the crash, I disabled the survey monkey from being able to pop up, and fortunately could still right-click and open a new tab, then pick one of the thumbnails (thank God they were there) and then open it in a new window, which brought back the menu and all the Firefox controls.
But now, this weekend, it happened over and over whenever a I put a streaming Youtube movie on long pause (long enough for the monitor to turn off), using two monitors, with either Chrome or Firefox being the window to stream the Youtube movie in the TV, which is secondary in my setup. This has NEVER happened before, and I've had them operating like this often, for years.
BSOD message was 0x0000000F4, which is usually something you sleuth for days to figure out, since it's supposed to be hardware related and semi-serious. Started up in Safe Mode just fine when I finally unplugged the TV so only one monitor could be used. Until then, the errors kept changing.
But when starting up Firefox, same problem as in red text above. So then it had to be the About:newtab. So, I disabled it.
Now everything seems fine, but more testing is needed.
If it matters, the full error message was 0x000000F4 0x00000003 0x88636478 0x886365E4 0x82E61430 . I type this out fully, as searching on that error brought nothing. Only the many variant reasons for an F4 error, which could have cost me precious days to troubleshoot. Happily, since the Firefox error was the same as prior, I knew to disable about:newtab, first.
Will keep testing. Hope this helps save time for someone else.
Edited by brainout, 20 September 2015 - 11:17 PM.