If I'm following correctly and the problem began after the update manager did updates then of course the problem is in one of the programs that was updated; but the conflict could be with hardware or software, not enough info given to say. Was the kernel also updated. Could be your computer has issues with the latest kernel or that the kernel isn't the latest.
I'm weighing in because I know from first hand experience that you could be exacerbating your problem when the computer freezes by "rebooting it by hard reset," that's not good and should only be done in the extreme. Here are some tips you can use when Ubuntu freezes:. a) ctrl - alt - backspace will restart the X server, kill all processes by pressing alt - sysRq - K , c) add to panel has a force quit shortcut that can be placed there, d) Go to System - Administration - System Monitor and then in the Processes tab and select the application you believe to be causing the freeze. Obviously, choice D is also a good way to diagnose if a particular piece of software is at the root of your problem. After writing all this I found this webpage maybe it says what I said even clearer. http://www.maketecheasier.com/4-ways-to-get-yourself-out-of-a-ubuntu-crash/2008/09/01
A quick fix to your problem (predicated on if I'm reading your problem correctly) is to boot from a kernel where your computer was running fine. Ubuntu has a number of how too's on this. ( I use GRUB CUSTOMIZER). From the older kernel you can also run updates again and make note of what applications are to be updated along with the new kernel. You don't need to install all the updates at the same time, in small #'s so you can check for problems. You should check with Ubuntu to see if there are any known issues with your model computer, graphics card, etc. I hope I was helpful.