Open your file manager as root and go to /usr/share/applications/
Find the google .desktop file and right click on it an open it in an editor like mousepad.
It should look something like this...
GenericName=3D planet viewer
Comment=Explore, search and discover the planet
What your interested in is the line that starts Icon=
There you need to make sure the path to the icon is correct.
Open catfish and search google .png
Search the filesystem folder.
Catfish will locate the file and define the correct path for you, put that in the line that starts 'Icon=' in the .desktop config file.
This is all based on the assumption that you are using VL 5.9 gold. If not please let us know the version you are using.
Hope it helps.