Excel says "The file is corrupt and cannot be opened", but the file is not corrupted.

Doesn't seem anyone is interested in this discussion - but I also have the same problem.  The first time I try to open an Excel 2016 file it tells me it is corrupted and cannot be opened.  When first opening it only goes to "processing" and then the message.  I then close down the resulting blank excel sheet plus a "ghost" sheet Excel creates with nothing there, not even a grid.  Then I go and open the file a second time and everything opens ok.  This is on any file I try to open. 

Eventually sometime during the day Excel then locks up and I have to shut Excel down and start again.  Its very annoying, but doesn't seem to be solvable.  Trusted Sites does not solve this.