After recently using the Migration Assistant to transfer almost my entire late 2009 iMac data to my new late 2014 iMac, I found that Google Drive wouldn't work properly. Scratch that - wouldn't work at all...
The program would not launch, wouldn't show the icon in my toolbar, and it would only take my to my local Google Drive folder. After some digging, here's what I found.
You simply need to delete the following entire folder:
(Alternatively, if you know your way around Terminal, you can use the following:
sudo rm -r -f ~/Library/Application\ Support/Google/Drive/)
Once you delete that folder, launch the app again. This time it should ask you for your Google credentials and you'll be back up and running!
Hope this helps!
These instructions were created on Jun 12, 2015.
I am running OSX 10.10.3 (Yosemite)