I spent an hour and half with customer support and then my spouse spotted the issue.   I could not save any new invoices once I imported the consultants time.  I repeatedly got the error message "Something you're trying to use has been made inactive. Check the fields with accounts, customers, items, vendors or employees"

The issue had nothing to do with the error message... the fix was in the tax rate line.   You are forced to chose a tax rate, even if your product is non taxable.    Our services are non taxable so we had been selecting "out of scope" - once we chose an artificial tax rate.. the invoice would save correctly.