"Identify Label" bug when using INDEX/MATCH and VLOOKUP formulas
 

I never had this issue before today:
When I used INDEX/MATCH and VLOOKUP formulas this morning (formulas that I
have used successfully and without incident thousands of times) I received a
dialog box asking me to identify the Label. I pressed "Cancel" and then
Excel shut down. I have received the same outcome every time I have used
these formulas since then.
I have disabled "Accept labels in formulas" in the Options---Calculation
menu and also disabled all Add-ons but I still get this error.
I have not found any useful information on how to correct this.
Please let me know how to reconcile this. Thank you.