I just thought this might help someone else.
When creating the VirtualBox machine for Linux Mint 16 you can either have
Type: Linux, Version: Ubuntu
Type: Linux, Version: Linux 2.6/3.x
I couldn't find any documentation on what selecting Version: Ubuntu did for you, so I just selected Version: Linux 2.6/3.x
Then I tried loading the Linux Mint 16 KDE 32bit iso. And it hung. When I finally tried compatibility mode, I got an error about PAE. I hadn't realized this, but that is a setting for the VirtualBox VM under System|Processor tab there is a checkbox Enable PAE/NX.
It turns out that if you select Version: Ubuntu, this checkbox is checked for you, if you select Linux 2.6/3.x you need to check it yourself in order for the 32bit version of Linux Mint to run.
I do remember seeing something about PAE in the release notes, I just didn't really know what it meant, or how it might affect me.