Nexus 7 - Security Setting

I installed an app VPN one click and for that I had to setup a PIN for "Screen lock".

This page explains how to set the screen lock. However since then I wasn't able to change the Screen lock to "Slide" (None, Slide and Face Unlock were grayed out).  Instead I needed to keep putting in the PIN.

I had to remove the VPN profiles, and that allowed me to see and choose one of the other options again.