I thought I had updated to the latest version of PHP a few days ago, I went back and double checked…the upgrade never occurred and I was still on 5.4. Updated to PHP Edge so I should get the latest and greatest as it’s released.
So after a little more troubleshooting. It seems the issue is/was not the “Google Tag Manager for WordPress” Version 1.6.1 plugin, a least not on it’s own anyway. I found another plugin that doesn’t seem to be playing nice with my site overall. My site now loads with the “Google Tag Manager for WordPress” Version 1.6.1 plugin enabled.