To be sincere I haven't used Google Earth for a while but after I repeat some steps that you've done I experienced some issues with version 6 too. I'm also running 12.04 and this what I did to fix this:
Remove everything that belongs to Google Earth currently installed, I advise you to use Synaptic open it and type
Google Earth click on marked item area and from pop up menu choose
complete removal after it removed close Synaptic.
Now open a terminal Ctrl+Alt+T and run:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get autoremove
(let it to remove listed packages)
Now go to your
/home press Ctrl+H find folders
.config search for Google Earth in them and delete everything, for now we're done.
Go back to terminal and install
sudo apt-get install gdebi
Ok, now download Google Earth 7
.deb file, when download is done, type in terminal:
sudo gdebi /home/yourname/Downloads/packagename.deb
hit Enter then type
y and hit Enter again.
or go manually to a downloaded file directory and on a file mouse right click and choose install with
gdebi in opened window click
install package and agree to whatever comes out. Done.
When installation has been completed reboot the system, for some reasons I also experienced loading issues with Google Earth to start, so after a clean restart everything works perfectly fine, I closed it and opened it twice, it starts without problems and the search bar works too.
This workout works on 12.04 perfectly, so good luck!