Google Drive for OS sometimes unable to connect (not a problem in latest versions)
If you are using a MacBook, you are most likely experiencing this error because Google Drive has a tendency to have connection problems when the computer is woken from sleep. I noticed this happening to me on several occasions when I open my computer up in class, particularly when the wifi takes a while to connect.

Although there is not much you can do about the bug itself, I have found that it is much less likely to happen if other internet-connected apps open.