In my laptop I had installed google earth before I install GS and it was  working great. The same thing with two other laptops that running  Windows XP .
From the moment I install GS, google earth never running properly again. I  remove everything from control panel add/remove programs (GS4.0.6,  googlearth plugin, google earth, even .net framework) many times and I  install them again from the beginning with the right order, with  different order,  only the google earth , but  Google earth never worked  properly again.The same thing with the two other laptops that running  Windows XP . 
Then I remove everything from pc , reboot and I install only Google Earth.Ti is not working again. When I tried to uninstall it I saw Chinese letters to the popup!That's why I conclude there is something wrong with GS. 
By the way what OS are you using (Windows XP or Windows 7)? Because I thinking to buy a new netbook running Win7.