Using New Outlook on Windows for professional communication and productivity
Now here is something new. I posted to a previous response that you could still use the older version. Now my older version won't work. As soon as it loads, it quits. If you try to reload, it asks if you want to start in "safe" mode. If you say yes, it will start in safe mode, but if you close it and restart it in normal mode, it quits again. I wonder if MS has don something to disable the old version to force the use of the new one.
This article has instructions to revert to Windows mail or Outlook for Windows - check the registry settings and see if that helps.
Working in Safe mode means one of the support files or addins is causing problems. I would probably try starting Outlook with the /resetnavpane
Close Outlook. Right-click on the Start button and choose Run or press Windows key + R to open the Run command.
Type or paste the following into the Open field and press Enter or click OK to restart Outlook. (There is a space before /.) outlook.exe /resetnavpane
This will wipe out all folders on Favorites in Mail module and reset the Calendar and Contacts modules to the default format.
Actually, since I have an extensive favorites mail list, I would rename the Outlook folder at %appdata%\microsoft and see if it fixes it. If yes, best guess is the XML file for the folder pane is the problem. If it doesn't fix it, I can get the favorites back after by deleting the new Outlook folder and changing the name on the old one back.