Google Drive appears to be having a major outage, currently. We are monitoring the situation and will post updates as we have them.
This is possibly related to a massive e-mail phishing/virus spreading through Gmail/Google Docs.
Details are currently sketchy, but if you get an invitation to access a shared Google Doc from anyone, including a known contact, DON’T open it, at least until this stuff is sorted out.
Google reports that the issue with Google Drive is now resolved.
There still isn’t a whole lot of information on the phishing scam, but this reddit thread has some of the best info so far, for those interested or affected: https://www.reddit.com/r/google/comments/692cr4/new_google_docs_phishing_scam_almost_undetectable/