It depends on the version of earth you are using.
With the "stand-alone" version: https://www.google.nl/earth/download/gep/agree.html
Go to Options > Cache and then Remove cache (Both)
If that does not help go to Options > 3D and check DirectX (or any other to see the effect) and restart the program to apply the changes.
If it still does not work go to the download page and chose an older version, it is possible that you computer is not compatible with the latest version.

Rob