Thanks for the assistance fellas. Turning off hardware acceleration didn't have a noticeable impact.
I ended up using Microsoft Support and Recovery Assistant for Office 365 (https://support.office.com/en-ie/article/uninstall-office-from-a-pc-9dd49b83-264a-477a-8fcc-2fdf5dbf61d8) to purge and then installed again from scratch. Worked as expected right away again...
One of my Office 365 users has a situation where any .xls or .xlsx crashes whenever Protected View is launched.
This occurs for any spreadsheet from email or web site, thus isn't trusted.
Host OS is Windows 7 (workgroup) and I can right click the files, unblock in properties where it says "This file came from another computer and might be blocked to help protect this computer" and then they open fine, of course not in Protected View. Most solutions I've found online are simply disabling Protected View and I don't wish to do that.
This is the offline version of 365 and I have reinstalled, same thing. Next step, I'm going to completely remove office and try installing again, but has anyone else encountered this?