Am relating my experiences here in the hope that it helps someone.
I was happily running VirtualBox 4.1.2 on Windows 7 64-bit, with connectify.me.
When VirtualBox 4.1.4 was released, my problems started. The installer for 4.1.4 uninstalled 4.1.2 properly, but it couldn't install properly, hanging at around the 80% mark (on the progress bar), without any error messages or CPU/hard-disk activity. The installer was still listed in the task manager, and could be terminated gracefully. However it simply refused to complete.
On a gut feel, I uninstalled connectify.me, went through the requisite reboots, and the subsequent installation of Virtualbox 4.1.4 went without a hitch.