If Google Drive is having trouble opening a document you uploaded recently, it may be a trust issue. Example: a coworker sent you a spreadsheet which you downloaded to your desktop, uploaded to Google Drive, and then tried to open. Upon opening you receive the following message:
The issue is that the document has not been marked as a trusted document. Before uploading it to Google Drive, open it locally. At the top, you'll see a message warning you of the dangers of downloaded files:
Assuming the file is from a trusted source (e.g. said coworker), you need not fear. Click the "Enable Editing" button, and close the document. Now upload it to Google Drive again and try opening. Because the document has been marked as clean and trustworthy, Google Drive should have no trouble opening it up.