Shell mode for this user opened just fine with no errors. Other users were able to open BOTH the Shell and the Classic view with no issues.
I deleted all of the problem-user's personalizations through the Customization Maintenance program, cleared their Client Cache (which can be found in Home-Settings in Shell mode for those of you looking for that), deleted all Favorites (that were visible...more on that later!) from the Shell view listing, deleted all of their History and tried unchecking some options under the settings to try to revert this user to a sort of base or new user account just to see if I could finally get them logged into the Classic view this way. (BTW, this was a TEST system so I could get away with all of this....) I also followed this post's suggestion of running the Personalization Purge which I didn't know existed till now. I thought Customization/Personalization maintenance would take care of all personalizations but I did find some additional personalizations that were related to the MainMenu Layout and History in the Purge search for this user.
Doing all of these things changed something because I was finally able to log this user into the Classic View! I did, however, still receive an Application Error Message that said:
Exception caught in: Ice.Menu.Main.
Error Detail: Object reference not set to the instance of an object.
Program: Ice.Menu.Main.dll
Method: loadShortcuts
I was able to click OK and bypass this error and the Classic view would still open.
To get rid of the error above I looked at the Favorites in the Classic view and saw that there was still one Favorite sitting in my list. I thought I had deleted them all from the Shell Favorites listing but I don't think it ever showed up there. It was an Internet Explorer link to a Website. So I deleted it and now Classic View for the user is opening without error!
So it almost seems as if not all favorites (especially "outsider" ones?) are showing up in Shell view. Maybe there needs to be a Favorites Purge or Maintenance module of some sort? It would be nice to be able to search a list of someone's favorites and for each item be able to delete it or modify it or even trace it back to it's original location. That way if someone has renamed a Favorite link you can track it back to where it came from on the Epicor menu....but I digress.....just wanted to share my experience and hope it helps someone else. Thanks! :)