Tried everything (turning off hardware acceleration, ignore DDE, repair, KB2994633 etc) but none of it worked.
The Windows Explorer Preview pane showed the xlsx file fine but Excel showed a blank gray screen.
My solution:
- Double click the problematic Excel file
- Go to View tab in Excel
- Click on Unhide - a window appeared to me where I could select to
Unhide workbook.
- Voila! :)
I had to re-save / overwrite the file to make the solution permanent. Perhaps if anyone has the same problem, take a backup of the problematic file and send it to Microsoft so they solve this problem once and for all.
I wasted 2½ hours on this - and even installed Office Configuration Analyzer but that did not help either.
Running Windows 10, Excel 2013 with all the latest updates as of Nov 10th 2015.