This problem seems to affect 32 bit version of Ubuntu. I just realized my working xubuntu install was 64 bit as opposed to the 32 bit I was using for Ubuntu. So I decided to try out 64 bit Ubuntu and guess what? Shuts down and reboots as expected every single time and I've been using for a couple of days and have not experienced any hangs.
This problem seems to affect 32 bit version of Ubuntu. I just realized my working xubuntu install was 64 bit as opposed to the 32 bit I was using for Ubuntu. So I decided to try out 64 bit Ubuntu and guess what? Shuts down and reboots as expected every single time and I've been using for a couple of days and have not experienced any hangs.