This is a new error in QBO which has been reported to our engineers, jlmconstruction2.
You'll get this error when trying to save an invoice using the Progress Invoicing feature. The suggested work around is to create an invoice from a regular estimate. To do this, you'll have to turn off Progress Invoicing first.
I highly suggest that you subscribe to get updates on this issue. Just give us a call and we'll add you to the list of affected users. You'll receive an email when there's an available solution.
Thank you for your patience. Please let me know if you need anything else.