OMG, LG is the biggest POS ever, I'll never buy another again.
So apparently there's a new version of plex on their site which fixes the issue. So I'm sitting here downloading it, getting ready to install it, and I had launched the old server version just to confirm what version it was. While I'm sitting there, the TV starts rebooting again and...
MY PICTURE IS UPSIDE DOWN NOW!
Yes, really, the TV image on the screen is now upside down. Tried turning the set off and on, no change. Tried launching plex again to see if a couple of reboots would jog it back, no dice. Time to call LG now.
AMP, it's like MSG for your TV!