I found the solution today after 3-4 days of looking. So I recently got a GTX760 and after just 15-20 minutes of gameplay I used to get BSOD. I tried everything, updated every driver, changed to a different HDD, ran memtest, cleaned out dust, uninstalled the usb ports and reinstalled everything, ran on a fresh windows install.
The problem is with latest Nvidia driver versions: 320.18 and 320.49 + All the new beta after 320.49.
The problem I noticed here is that most people with the gtx 760 are having this problem of BSOD and those crashes and freezes while running firefox. Even greater problem here is that any driver before 320.18 were released before 760,770 & 780 GTX series came out so installing those older drivers doesn't normally work because those drivers do not detect these cards. So we are stuck with only those options for drivers which are faulty and hence we are not able to solve the problem.
Now the trick here is to hack the INF of the older drivers(314.22 is the best, I'm using it now), and make them detect your 700 series cards.
You can get 64bit 314.22 version drivers from: http://www.nvidia.com/object/win8-win7- ... river.html
Get the program "7zip" and right click the driver .exe and extract it to a folder. Inside you'll see a folder named "Device.Driver", go inside that driver and replace the original file with the one I have attached below.
This file is already edited to detect your 700 series cards and all you need to do after copying it is run the setup and the drivers 314.22 will be installed even on your 700 series cards:
Now after this I played Assassins Creed 3 for a long enough time. The BSOD might return, can't say for sure but this has probably made the crash happen at after a longer time + fixed some issues. Earlier in my Review and First Impression thread about gtx 760, I talked about Assassins Creed 3 being unplayable on my PC due to CPU being a bottleneck but now I can actually run it over 30 fps in Boston too. Earlier it was 20 or below in Boston so seems like the driver version 314.22 are a better choice over the 320.49 if you're using a 700 series card. This does not happen to everyone with 700 series cards but it does seem many people are having the issue.
UPDATE 1 : Played Bioshock Infinite for a long time, over 2 hours. NO BSOD. So I guess the problem is fixed + the fps improved by 10 but loading time has increased compared to before + lag when loading a new area etc. but I guess that might be my cpu, this lag and loading time was less with 320.49 drivers but overall fps in gameplay was 10 fps slower than the 314.22.
UPDATE 2 : Played Tomb Raider for a good amount of time, no crashes or BSOD. Ran benchmark tool, only about 2 fps increase over the previous benchmark I did -> viewtopic.php?p=9474