LOL, nice one.....I though it was F12 - which didnt work! Brain was fizzed from figuring out the issue, which BTW (Dun Dun Duuuuuuuuun) I figured it out, graphics needed for horizons were set too high, had to drop my expectations.....
I had this first time I went into live horizons build.
I reset my graphics settings lower.
I also disabled windows aero and ran on windows basic
enabled shader warming option
turned off ambient occlusion
made sure draw distance bar was to the left of centre of the available range
terrain quality medium, terrain material quality low.
terrain work bar the farthest left it would go
Anti aliasing off
everything else medium setting were possible
next time I started game was fine and dandy.
Make sure your running latest drivers by visiting either the AMD or NVIDIA sites. Don't rely on automatic windows updates as these are often somewhat out of date.